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CCNA Routing Fundamentals Questions

60 questions · Routing Fundamentals · All types, answers revealed

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1

MCQmedium

An administrator executes 'show route 192.168.1.0/24' and sees no output, but the route is configured. Which command should be used to display the reason the route is not active?

A.show route hidden

B.show log messages

C.show route protocol static

D.show route forwarding-table

AnswerA

The `show route hidden` command is the definitive way to view routes that the routing table has marked as unusable, along with the specific reason for their hidden status. Junos maintains hidden routes in the routing table (e.g., inet.0) but excludes them from active forwarding and from normal `show route` output. This command directly reveals those routes and the `hidden` reason field, enabling targeted diagnosis. It is the only command listed that fully exposes hidden routes without additional filters.

Why this answer

The 'show route hidden' command displays routes that are present in the routing table but are not active due to reasons such as a next-hop being unreachable, a routing policy rejecting the route, or a route preference conflict. When a route is configured but not shown in the standard 'show route' output, it is likely hidden, and this command reveals the specific reason (e.g., 'next-hop unreachable' or 'rejected by policy').

Exam trap

The trap here is that candidates assume 'show route protocol static' will show all static routes, but they forget that hidden routes are excluded from standard protocol-specific outputs, leading them to overlook the dedicated 'show route hidden' command.

How to eliminate wrong answers

Option B is wrong because 'show log messages' displays system log messages (e.g., interface flaps, errors) but does not show hidden routes or the specific reason a route is inactive. Option C is wrong because 'show route protocol static' filters the routing table to show only static routes, but if the static route is hidden, it will not appear in this output either; it does not reveal why the route is hidden. Option D is wrong because 'show route forwarding-table' displays the kernel forwarding table (used for packet forwarding), not the routing table, and does not show hidden routes or reasons for inactivity.

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2

MCQeasy

A router has an OSPF route to 10.10.10.0/24 with preference 10 and a static route to the same prefix with preference 5. Which route is active in the routing table?

A.The OSPF route

B.The static route

C.Neither route

D.Both routes

AnswerB

The static route is correctly identified as the active route because Junos assigns it a default preference of 5, which is lower than OSPF's default of 10. A lower preference value indicates a more trustworthy route, so the static route wins the route selection process. Consequently, the static route is installed in both the routing table (inet.0) and the forwarding table, and it will be used for packet forwarding. If the static route is later removed, OSPF can take over, but as long as both exist, the static route remains preferred.

Why this answer

In Junos, the active route in the routing table is determined by the route preference (administrative distance). A lower preference value indicates a more trusted route. Here, the static route has a preference of 5, which is lower than the OSPF route's preference of 10, so the static route is preferred and becomes active.

Exam trap

The trap here is that candidates familiar with Cisco's administrative distance (where OSPF is 110 and static is 1) might assume OSPF is preferred, but Junos uses lower preference values to indicate higher trust, and static routes default to 5, which is lower than OSPF's 10.

How to eliminate wrong answers

Option A is wrong because OSPF has a default preference of 10, which is higher than the static route's preference of 5, so the OSPF route is not selected. Option C is wrong because one route must be active; the router will always choose the route with the lowest preference for a given prefix. Option D is wrong because Junos installs only the best (lowest preference) route into the forwarding table; both routes cannot be active simultaneously.

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3

MCQeasy

A network engineer is troubleshooting a connectivity issue and wants to see the active routes in the routing table. Which Junos CLI command should they use?

A.show log messages

B.show configuration

C.show interface

D.show route

AnswerD

The 'show route' command is the correct tool for troubleshooting a connectivity issue because it displays the active routing table, including all routes learned from each routing protocol, with their next-hop addresses and preference values. It allows an engineer to verify whether a destination is reachable, which route is being used, and why that route was selected. This command directly answers whether the router has a valid forwarding path to the target network.

Why this answer

The 'show route' command displays the active routing table entries, including directly connected, static, and dynamic routes learned via protocols like OSPF, BGP, or IS-IS. This is the correct command to view the active routes the device uses for forwarding traffic.

Exam trap

The trap here is that candidates familiar with Cisco IOS might confuse 'show ip route' with Junos's 'show route' but incorrectly choose 'show configuration' thinking it shows routing information, or 'show interface' thinking it shows connected routes, when only 'show route' provides the complete active routing table.

How to eliminate wrong answers

Option A is wrong because 'show log messages' displays system log messages (syslog) for troubleshooting events, not the routing table. Option B is wrong because 'show configuration' displays the current configuration, not the operational routing table. Option C is wrong because 'show interface' displays interface status and statistics, not routing information.

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4

MCQmedium

A router has two routes to the same destination: one with preference 10 and metric 5, and another with preference 15 and metric 3. Which route will be installed in the forwarding table?

A.The route with preference 10.

B.The route with metric 3.

C.Neither route is installed.

D.Both routes are installed if ECMP is enabled.

AnswerA

Junos evaluates preference before metric, so the route with preference 10 wins even though its metric of 5 is worse than the alternative's 3. Metric only breaks ties between routes of equal preference, so the lower-preference route is never compared and the preference-10 route enters the forwarding table.

Why this answer

In Junos, the route preference (administrative distance) is the primary criterion for selecting the best route to a destination. The route with preference 10 is preferred over the route with preference 15, regardless of metric values. The route with preference 10 is installed in the forwarding table.

Exam trap

The trap here is that candidates often confuse metric with preference, assuming a lower metric always wins, but Junos prioritizes preference over metric in route selection.

How to eliminate wrong answers

Option B is wrong because metric is only used as a tiebreaker when preferences are equal; a lower metric (3) does not override a higher preference (15). Option C is wrong because one route will always be installed when there are valid routes to the same destination, unless both are rejected by policy or have the same preference and metric with ECMP disabled. Option D is wrong because ECMP (Equal-Cost Multipath) requires routes to have equal preference and equal metric; here preferences differ (10 vs 15), so ECMP does not apply.

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5

MCQmedium

A static route is configured with next-hop 10.0.0.1, but the route does not appear in the routing table. The interface ge-0/0/0 has IP 192.168.1.2/24 and is up. What is the most likely reason?

A.The static route has a preference of 5.

B.The route is hidden due to an import policy.

C.The static route is configured with the 'discard' option.

D.The next-hop IP is not on a directly connected subnet.

AnswerD

For a static route with an IP next hop to be installed in the Junos routing table, that next hop must be directly reachable via one of the router's connected interfaces. If 10.0.0.1 does not belong to any subnet configured on the router, the route cannot resolve the next-hop MAC address and remains hidden. Without the 'resolve' option, Junos does not perform recursive lookup, so the route is not installed; this matches the symptom exactly.

Why this answer

D is correct because Junos requires the next-hop IP of a static route to be reachable via a directly connected subnet for the route to be installed in the routing table. Since the next-hop 10.0.0.1 is not on the same subnet as the interface ge-0/0/0 (192.168.1.2/24), the route remains hidden and does not appear in the routing table.

Exam trap

The trap here is that candidates often assume any IP address can be used as a next-hop for a static route, but Junos strictly enforces that the next-hop must be on a directly connected subnet unless recursive resolution is explicitly configured.

How to eliminate wrong answers

Option A is wrong because a preference of 5 is actually lower (more preferred) than the default static route preference of 5, so it would not prevent the route from appearing; in fact, it would make it more likely to be installed. Option B is wrong because import policies affect routes learned from routing protocols, not locally configured static routes; static routes are not subject to import policies unless explicitly filtered with an export policy on the forwarding table. Option C is wrong because the 'discard' option would still install the route in the routing table as a discard route (with next-hop 'discard'), not hide it entirely.

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6

MCQeasy

An engineer wants to configure a static route that will be used only if the primary route (learned via OSPF) becomes unavailable. Which feature should be used?

A.Floating static route with a higher preference.

B.Static route with a lower metric.

C.Reverse path forwarding.

D.Routing policy.

AnswerA

A floating static route is configured with a higher preference value than the dynamic protocol's default. Since OSPF's default preference is 10, setting the static route's preference to, say, 15 ensures it is only used when the OSPF route is unavailable. This makes it a backup route.

Why this answer

A floating static route is configured with a higher preference (administrative distance) than the OSPF-learned route. Since JUNOS prefers routes with lower preference values, the static route will only be installed in the routing table when the OSPF route is withdrawn, providing a backup path.

Exam trap

The trap here is that candidates often confuse 'metric' with 'preference' (administrative distance), assuming a lower metric on a static route would make it preferred over OSPF, but metric only applies within the same routing protocol, not between different sources.

How to eliminate wrong answers

Option B is wrong because metric is used by dynamic routing protocols (like OSPF cost) to compare routes within the same protocol, not to influence route selection between different protocols; a static route with a lower metric does not affect its preference over OSPF. Option C is wrong because Reverse Path Forwarding (RPF) is a unicast or multicast forwarding security feature that verifies the source address of incoming packets, not a mechanism for route redundancy or failover. Option D is wrong because routing policies can manipulate route attributes or filter routes, but they do not directly create a backup static route that automatically activates only when the primary route is lost; the concept of a floating route relies on preference values, not policy alone.

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7

Drag & Dropmedium

Order the steps to reset the root password on a Junos device via the console.

Drag or tap steps into the slots.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

Why this order

Root password recovery requires boot interruption and selecting the recovery option from the boot menu.

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8

Multi-Selecteasy

Which TWO statements about static routes in Junos OS are correct? (Choose two.)

Select 2 answers

A.Two static routes to the same destination with the same preference will result in an active/backup scenario.

B.A static route can have a next-hop specified as an interface name for point-to-point interfaces.

C.A static route can use the 'reject' next-hop to drop traffic matching the route.

D.The default preference for a static route is 10.

E.A static route must always include a next-hop address.

AnswersB, C

In Junos, a static route may specify an interface name as the next-hop, but this is valid only for point-to-point interfaces such as serial links. Because a point-to-point interface has exactly one remote endpoint, an explicit next-hop IP address is not required. The router will use the interface directly to forward matching traffic. This flexibility allows simpler configuration on such links.

Why this answer

Option B is correct because in Junos OS a static route may specify a next-hop as an interface name (for example, set routing-options static route 10.0.0.0/24 next-hop ge-0/0/0.0), which is valid and commonly used on point-to-point interfaces such as PPP, HDLC, or GRE tunnels where no remote address resolution is needed. Option C is correct because Junos supports the reject next-hop (set routing-options static route 10.0.0.0/24 reject), which installs a route that discards matching traffic and returns an ICMP unreachable message to the sender, unlike discard which silently drops packets. Option A is wrong because two static routes to the same destination with equal preference are both eligible and, depending on next-hop type, can be installed as multipath (ECMP) or one selected by tie-breaking, not an automatic active/backup pair; active/backup requires different preferences.

Option D is wrong because the default preference for static routes in Junos is 5, not 10 (10 is the default for OSPF internal routes). Option E is wrong because a static route does not always require a next-hop address; it can instead use an interface name, a discard, reject, or receive next-hop, or be qualified with options such as no-readvertise.

Exam trap

The trap here is that candidates often confuse Junos default preference values with Cisco's (where static routes default to 1), leading them to incorrectly select option D, or they assume static routes always need a next-hop IP address, missing the valid interface-only next-hop for point-to-point links.

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9

MCQeasy

Refer to the exhibit. Why is the route for 192.168.1.0/24 hidden?

A.The route has a higher metric

B.The route has a lower preference

C.The route is not committed

D.The next-hop is unreachable

AnswerD

Junos marks static routes as hidden when the configured next-hop address cannot be resolved to an active outgoing interface or next-hop route. Because the destination 192.168.1.0/24 is unreachable through that next-hop, the routing protocol process retains the route but does not install it in the forwarding table, displaying it with the 'hidden' flag. This is the standard condition that creates hidden static routes.

Why this answer

A route is hidden in the JUNOS routing table when its next-hop is unreachable. The show route command displays only active routes; if the next-hop address is not reachable via any active interface or route, the route is suppressed (hidden) and not used for forwarding. This is a fundamental behavior of JUNOS route selection and differs from Cisco IOS, which may still display such routes.

Exam trap

The trap here is that candidates often confuse hidden routes with routes that are not committed or have a higher metric, but JUNOS specifically hides routes when the next-hop is unreachable, not due to metric or preference comparisons.

How to eliminate wrong answers

Option A is wrong because metric (cost) is used for comparing routes from the same protocol to the same destination, but a hidden route is not hidden due to a higher metric—it is hidden because the next-hop is unreachable. Option B is wrong because preference (administrative distance) determines which route is active among different protocols, but a lower preference would make the route more preferred, not hidden; a hidden route is not caused by preference values. Option C is wrong because the route is committed (it appears in the configuration and is present in the routing table as a hidden route), but it is not active due to next-hop unreachability, not because it was not committed.

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10

MCQeasy

An administrator configures a static route to 192.168.2.0/24 with next-hop 10.0.0.1. The route does not appear in the routing table. What is the most likely cause?

A.The next-hop 10.0.0.1 is not reachable.

B.The static route has a higher preference than an existing dynamic route.

C.The configuration was not committed.

D.The prefix 192.168.2.0/24 already exists in the forwarding table.

AnswerA

A static route only installs when its next-hop resolves through a reachable interface. If 10.0.0.1 sits on no connected or otherwise resolvable subnet, the device cannot determine an egress interface, so the route stays inactive and never enters the routing table.

Why this answer

A static route will only be installed in the routing table if the next-hop address is reachable via an active route in the routing table. If 10.0.0.1 is not reachable (e.g., no route to that subnet, or the interface is down), Junos will reject the static route and not place it in the inet.0 table. This is a fundamental validation check in Junos that prevents black-hole routing.

Exam trap

The trap here is that candidates assume a static route is always installed immediately after configuration, forgetting that Junos requires the next-hop to be reachable via an existing route in the routing table before the static route becomes active.

How to eliminate wrong answers

Option B is wrong because preference (administrative distance) only matters when comparing routes to the same destination prefix; if the static route does not appear at all, it is not being suppressed by a more preferred route—it failed the next-hop reachability check. Option C is wrong because if the configuration were not committed, the route would not appear in the running configuration, but the question states the administrator configured it; a missing commit would mean the route is not in the candidate config, not that it fails to appear in the routing table. Option D is wrong because the forwarding table is derived from the routing table; if the prefix already existed in the forwarding table, it would have come from a route in the routing table, and a static route to the same prefix could still be installed (with a different preference) or could be rejected only if it were less preferred, but the primary issue is next-hop reachability.

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11

MCQmedium

An engineer observes that traffic destined to 203.0.113.0/24 is being load-balanced across two equal-cost paths via OSPF. The engineer wants to ensure that all traffic for this prefix uses only one path unless the primary path fails. Which configuration change should be made?

A.Configure a static route for 203.0.113.0/24 with a lower preference.

B.Set the OSPF metric on the backup interface to a higher value.

C.Use policy-options to set a higher preference for one of the paths.

D.Modify the load-balance configuration under forwarding-options.

AnswerB

In OSPF, the metric (cost) determines the preference of a route: lower total cost wins. By configuring a higher metric on the backup interface, the backup path's total cost becomes larger, so OSPF installs the lower-cost primary path in the forwarding table. The backup path remains in the OSPF database and is immediately used if the primary path disappears, preserving dynamic failover. This is the standard method to create an active/backup topology while keeping OSPF's adaptive behavior intact.

Why this answer

Increasing the OSPF metric on the backup interface makes that path less preferred in the SPF calculation, breaking the equal-cost multipath (ECMP) condition. OSPF selects routes based on the lowest metric; by raising the metric on one interface, the engineer ensures only the lower-metric path is used for forwarding, with automatic failover to the backup path if the primary fails.

Exam trap

The trap here is that candidates mistakenly think modifying load-balancing or preference settings can break ECMP, but OSPF ECMP is solely determined by equal metric values; only changing the metric directly controls path selection.

How to eliminate wrong answers

Option A is wrong because configuring a static route with a lower preference (administrative distance) would override the OSPF-learned route entirely, but static routes do not dynamically fail over; they lack OSPF's link-state awareness and would require manual intervention or additional tracking to handle failures. Option C is wrong because policy-options can modify route preference (administrative distance) for OSPF routes, but preference is not used in OSPF's SPF metric-based path selection; changing preference would affect route selection among different protocols, not ECMP within OSPF. Option D is wrong because modifying the load-balance configuration under forwarding-options (e.g., `maximum-paths`) controls how many ECMP paths are used, but it does not break the equal-cost condition; if both paths have the same metric, OSPF will still install them as ECMP unless the metric is changed.

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12

MCQmedium

A network administrator configures the following: `set routing-options static route 0.0.0.0/0 next-hop 192.168.1.1`. After committing, the administrator notices that the default route is not active. What could be the reason?

A.The route preference is set to 170.

B.The route is not exported into the forwarding table.

C.The next-hop 192.168.1.1 is not reachable.

D.The router already has a default route learned via DHCP.

AnswerC

For a static route with a next-hop address such as 192.168.1.1, the router must be able to resolve that address to a directly connected network or a route in the routing table. If 192.168.1.1 is not reachable—for example, because the subnet is not directly connected and no other route to it exists—the static route is considered to have an 'unresolvable next hop' and is kept inactive. Junos will not install an inactive route into the forwarding table, which directly explains the observed behavior. This is the most common reason a static default route fails to activate.

Why this answer

A static route becomes active only if the next-hop address is reachable via a directly connected interface or another active route. If 192.168.1.1 is not reachable (e.g., interface down, no matching subnet, or no route to the next-hop), the route remains hidden (inactive) in the routing table. Junos verifies next-hop reachability before installing a static route into the forwarding table.

Exam trap

The trap here is that candidates often assume a static route is always active once configured, overlooking Junos's requirement that the next-hop must be reachable for the route to be installed.

How to eliminate wrong answers

Option A is wrong because route preference (administrative distance) does not affect whether a static route is active; a preference of 170 is typical for BGP routes, not static routes, and even if set, it would only influence route selection among multiple routes, not activation. Option B is wrong because static routes are automatically exported into the forwarding table upon becoming active; no explicit export policy is required for static routes to appear in the forwarding table. Option D is wrong because the presence of a DHCP-learned default route does not prevent a static default route from being active; both can coexist, and route preference determines which is used, but the static route would still be active if its next-hop is reachable.

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13

MCQeasy

A network administrator is troubleshooting a missing route in the routing table. The route is learned via OSPF, and the OSPF neighbor adjacency is up. Which command would help determine if OSPF received the route?

A.show route protocol ospf

B.show ospf neighbor

C.show ospf database

D.show interface terse

AnswerC

The OSPF database command reveals the link-state advertisements (LSAs) stored in the router's OSPF LSDB, including Router, Network, and Summary LSAs that contain the actual prefix information. This is the authoritative source to verify whether a route's LSA has been received and is present in the network topology. If the prefix appears here but not in the routing table, the troubleshooting focus shifts to route selection or policy, making this the correct diagnostic step.

Why this answer

The OSPF link-state database (LSDB) contains all received LSAs, including Type 1 (Router) and Type 3 (Summary) LSAs that advertise routes. Even if a route is not installed in the routing table (e.g., due to a higher administrative distance or a missing route preference), the 'show ospf database' command confirms whether OSPF has received the LSA carrying that route. This directly answers the question of whether OSPF received the route, independent of route installation.

Exam trap

The trap here is that candidates often confuse 'show route protocol ospf' (which shows installed routes) with 'show ospf database' (which shows received LSAs), leading them to pick option A when the route is missing from the routing table but still present in the LSDB.

How to eliminate wrong answers

Option A is wrong because 'show route protocol ospf' displays only routes that are actually installed in the routing table, not all routes received by OSPF; a missing route in the routing table could be due to filtering or preference issues, and this command would not show it. Option B is wrong because 'show ospf neighbor' only verifies the adjacency state (e.g., Full) and does not reveal the contents of received LSAs or specific routes. Option D is wrong because 'show interface terse' shows interface status and configuration, not OSPF-specific route information or LSA details.

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14

MCQhard

A network administrator wants to filter routes from being installed in the routing table based on certain criteria. Which Junos feature should be used?

A.Community list

B.Routing policy (import)

C.Prefix list

D.Firewall filter

AnswerB

In Junos, the correct way to filter routes from being installed is to apply an import routing policy. An import policy is attached to a routing protocol or BGP group and is evaluated when routes are received; if a route does not match the policy's conditions, it is rejected and not placed into the routing table. This policy can also modify route attributes before installation, giving the administrator fine-grained control over what is learned and used for forwarding.

Why this answer

B is correct because a routing policy with an import term is the Junos mechanism to control which routes are accepted into the routing table from a routing protocol or a peer. By defining match conditions (e.g., prefix, community, AS path) and an action (accept or reject), the administrator can filter routes before they are installed. This is the standard Junos approach for route filtering at the routing table level.

Exam trap

The trap here is confusing a match condition (like a prefix list or community list) with the actual Junos feature that applies the filter (the routing policy), leading candidates to select a component rather than the complete mechanism.

How to eliminate wrong answers

Option A is wrong because a community list is a named set of BGP community values used as a match condition within a routing policy, not a standalone feature to filter routes from the routing table. Option C is wrong because a prefix list is a named list of prefixes used as a match condition within a routing policy, not a direct filtering mechanism for the routing table. Option D is wrong because a firewall filter operates on packets at the interface level (Layer 3/Layer 4), not on routing information or the routing table.

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15

Multi-Selecthard

Which THREE factors influence the selection of the active route in the Junos routing table when multiple routes exist for the same destination? (Choose three.)

Select 3 answers

A.Route preference (administrative distance).

B.The routing protocol from which the route originated.

C.Number of next-hops available for each route.

D.Metric value (if from the same routing protocol).

E.Bandwidth of the outgoing interface.

AnswersA, B, D

Route preference, also known as administrative distance, is a numerical value assigned to each route by the routing protocol. Junos always prefers a lower preference value, so a route with preference 5 (static) is chosen over a route with preference 10 (OSPF) for the same destination. You can alter these defaults to influence routing decisions. This is the first criterion in Junos route selection process.

Why this answer

Option A is correct because Junos uses route preference (the equivalent of administrative distance) as the primary tiebreaker: when routes to the same destination come from different sources, the route with the lowest preference value (e.g., Direct 0, Static 5, OSPF 10, RIP 100, BGP 170) is installed as active. Option B is correct because the route's originating protocol determines its default preference and thus directly influences which route wins when multiple protocols advertise the same prefix. Option D is correct because when multiple routes come from the same routing protocol (equal preference), Junos compares the metric and selects the route with the lowest metric as active.

Option C is not a selection criterion — Junos does not choose a route based on how many next-hops it has; multiple next-hops can be retained for load balancing only after a route is already selected. Option E is not a factor because interface bandwidth is not used as a tiebreaker in the Junos route selection process; metric values are protocol-specific and not derived from raw interface bandwidth.

Exam trap

The trap here is that candidates often confuse route preference with metric, thinking both are always compared, but Junos only compares metrics when routes originate from the same protocol (same preference), and never considers interface bandwidth or next-hop count in the selection process.

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16

MCQmedium

Refer to the exhibit. If the primary next-hop (192.168.1.1) becomes unreachable, what will happen to the route?

A.The route is removed from the routing table.

B.The route remains but with the primary next-hop marked as unreachable.

C.The secondary next-hop (192.168.2.1) will be used.

D.The route becomes hidden.

AnswerC

When the primary next-hop (192.168.1.1) becomes unreachable, Junos automatically selects the secondary next-hop (192.168.2.1) as the active forwarding next-hop because the secondary is configured as the fallback and is still valid. The route remains installed in the routing table and is forwarded via the secondary next-hop until the primary recovers and is preferred again.

Why this answer

In Junos, when a route has multiple next-hops configured (e.g., primary and secondary), the secondary next-hop serves as a backup. If the primary next-hop (192.168.1.1) becomes unreachable, Junos automatically fails over to the secondary next-hop (192.168.2.1) without removing the route from the routing table. This behavior is controlled by the 'next-hop' configuration under a static route or via routing protocol policies, ensuring continuous reachability.

Exam trap

The trap here is that candidates often assume a route is removed or hidden when a next-hop fails, but Junos maintains the route and uses the backup next-hop, unlike some other vendors that may withdraw the route entirely.

How to eliminate wrong answers

Option A is wrong because the route is not removed from the routing table; Junos retains the route and simply switches to the secondary next-hop when the primary is unreachable. Option B is wrong because the route does not remain with the primary next-hop marked as unreachable; instead, the primary next-hop is removed from the active forwarding path and the secondary next-hop is used. Option D is wrong because the route does not become hidden; hidden routes are typically those suppressed by routing policies or protocols (e.g., due to route summarization or BGP), not due to next-hop failure in a static route with a backup.

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17

Multi-Selecteasy

Which TWO statements are true about the default route in JunOS? (Choose two.)

Select 2 answers

A.It has a prefix of 0.0.0.0/0

B.It can only be learned dynamically

C.Its default preference is 0

D.It can be added via a static route

E.It is always present in the routing table

AnswersA, D

The default route is the quad-zero route, 0.0.0.0/0, which serves as a catch-all entry in the IPv4 routing table. This prefix matches every destination IP address because the /0 mask requires no bits to match, so any packet that does not match a more specific route is forwarded using this route. Its presence is the foundation of default routing, ensuring traffic to unknown destinations has a valid next hop.

Why this answer

Option A is correct because the default route in JunOS (and IP generally) is the all-zeros prefix 0.0.0.0/0, which matches any destination not covered by a more specific route. Option D is correct because a default route can be manually configured as a static route, e.g., 'set routing-options static route 0.0.0.0/0 next-hop <ip>', making it a common way to provide a gateway of last resort. Option B is wrong because the default route can be either statically configured or dynamically learned (e.g., via OSPF, BGP, or IS-IS), not only dynamically.

Option C is wrong because the default preference for a static route in JunOS is 5, not 0 (0 is reserved for directly connected routes). Option E is wrong because the default route is not automatically present in the routing table; it must be explicitly configured or learned.

Exam trap

The trap here is that candidates often confuse the default route's prefix (0.0.0.0/0) with its preference, mistakenly thinking a default route has a preference of 0 like a directly connected route, or assuming it is always present in the routing table.

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18

MCQmedium

A network is experiencing intermittent routing loops. The engineer discovers that routes are being redistributed from OSPF into BGP and then from BGP back into OSPF on different routers. What is the most effective way to prevent this?

A.Use a higher preference for BGP routes.

B.Configure route filters to prevent mutual redistribution.

C.Set a lower metric on OSPF routes.

D.Increase the OSPF cost on interfaces.

AnswerB

Configuring route filters is the correct fix because mutual redistribution loops occur when a route from protocol A is exported to protocol B, then re-imported into protocol A, creating a feedback cycle. Route filters can block this by matching on route tags, protocol origin, or prefix lists at the redistribution boundary, preventing a route from being re-advertised back into its source protocol. For example, tagging OSPF routes when redistributing into BGP and then filtering out that tag on the reverse redistribution breaks the loop.

Why this answer

Mutual redistribution between OSPF and BGP creates routing loops when routes are exported from OSPF into BGP on one router and then re-injected back into OSPF on another router. The most effective way to prevent this is to use route filters (e.g., prefix lists, route-maps, or policy-statement in Junos) to control which routes are redistributed, ensuring that routes learned from one protocol are not re-advertised back into the same protocol. This breaks the redistribution cycle without altering protocol preference or metrics.

Exam trap

The trap here is that candidates often think adjusting administrative distance or metrics can break redistribution loops, but only explicit route filtering (or tagging) prevents the cycle of mutual redistribution.

How to eliminate wrong answers

Option A is wrong because increasing the preference (administrative distance) of BGP routes would make BGP routes less preferred over OSPF routes, but it does not prevent the redistribution loop; the loop occurs due to re-injection of routes, not due to route selection. Option C is wrong because setting a lower metric on OSPF routes only influences OSPF path selection, not the redistribution process; it does not stop routes from being re-injected from BGP back into OSPF. Option D is wrong because increasing OSPF cost on interfaces affects OSPF link metric calculations and can change path selection, but it has no effect on redistribution policies or the prevention of mutual redistribution loops.

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19

MCQhard

A router receives two OSPF routes for 10.10.10.0/24: one intra-area with preference 10 and metric 1, and one external type 2 with preference 150 and metric 20. Which route is selected as active?

A.The external route because it is type 2

B.The intra-area route because it has a lower preference

C.The external route because it has a higher metric

D.The intra-area route because it has a lower metric

AnswerB

The intra-area route is the correct choice because Junos selects the route with the lowest preference value among all candidate routes for the same prefix. In this case, the intra-area OSPF route has a preference of 10, while the external OSPF route has a preference of 150; since 10 is lower than 150, the intra-area route is installed as active in the forwarding table. Preference is checked before metric—only when two routes share the same preference does the router compare metrics. Therefore, the lower preference of the intra-area route is the decisive factor, not the route type or metric.

Why this answer

B is correct because Junos uses route preference (administrative distance) as the primary tiebreaker when selecting the active route for a destination. The intra-area OSPF route has a default preference of 10, which is lower than the external type 2 route's preference of 150, so the intra-area route is installed into the routing table regardless of metric values.

Exam trap

The trap here is that candidates often focus on metric or route type (intra-area vs external) as the tiebreaker, but Junos strictly uses route preference first, and the large difference (10 vs 150) makes the intra-area route the clear winner regardless of metric values.

How to eliminate wrong answers

Option A is wrong because OSPF external type 2 routes do not have inherent priority over intra-area routes; route preference is the decisive factor, not route type. Option C is wrong because a higher metric does not make a route more preferred; in Junos, preference is evaluated before metric, and a higher metric is actually less desirable. Option D is wrong because while the intra-area route does have a lower metric, the primary reason it is selected is its lower preference (10 vs 150); metric is only considered if preferences are equal.

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20

Drag & Dropmedium

Order the steps to configure firewall filters (ACLs) in Junos.

Drag or tap steps into the slots.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

Why this order

Firewall filters are defined with terms (match conditions and actions) and applied to interfaces.

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21

MCQhard

Refer to the exhibit. The router has three static routes configured. Which route will be used to forward a packet destined to 172.16.1.100?

A.The default route (0.0.0.0/0)

B.The router will drop the packet.

C.The static route to 10.0.0.0/8

D.The static route to 172.16.0.0/16

AnswerD

The destination 172.16.1.100 lies exactly within the 172.16.0.0/16 network, and this is the most specific static route matching the destination. Junos applies the longest-prefix-match rule, so this route is selected to forward the packet toward its next hop. No other static route in the exhibit is more specific, making this the correct forwarding entry.

Why this answer

The router will use the most specific matching route for the destination 172.16.1.100. The static route to 172.16.0.0/16 has a prefix length of 16, which is more specific than the default route (0.0.0.0/0) and the route to 10.0.0.0/8 (which does not match the destination). Therefore, the route to 172.16.0.0/16 is selected based on the longest-prefix-match rule.

Exam trap

The trap here is that candidates often assume a default route will always be used as a catch-all, but they forget that a more specific static route (like 172.16.0.0/16) will take precedence over the default route for matching destinations.

How to eliminate wrong answers

Option A is wrong because the default route (0.0.0.0/0) is only used when no more specific route matches the destination; here, the 172.16.0.0/16 route is a better match. Option B is wrong because the router does not drop the packet; it has a matching route (172.16.0.0/16) and will forward the packet accordingly. Option C is wrong because the static route to 10.0.0.0/8 does not match the destination 172.16.1.100, as the destination falls outside the 10.0.0.0/8 range.

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22

Multi-Selecthard

Which THREE route types are considered protocol-independent in Junos?

Select 3 answers

A.BGP routes

B.Direct routes

C.Local routes

D.Static routes

E.OSPF routes

AnswersB, C, D

The direct route is automatically installed by Junos when you assign an IP address to an interface and it is operational. It represents the subnet directly attached to that interface, and its existence does not involve any routing protocol at all. This is why it is classified as protocol-independent.

Why this answer

Direct, local, and static routes are considered protocol-independent because they are not learned or installed by any dynamic routing protocol. Direct routes are automatically created for directly connected interfaces, local routes represent the interface's own IP address, and static routes are manually configured by an administrator. These routes exist in the routing table regardless of whether any routing protocol is running, hence the term 'protocol-independent'.

Exam trap

The trap here is that candidates often confuse 'protocol-independent' with 'routing protocol' and incorrectly assume that all routes in the routing table are protocol-dependent, forgetting that direct, local, and static routes are manually or automatically generated without a dynamic protocol's involvement.

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23

MCQhard

A route learned via BGP appears as 'hidden' in the routing table. Which condition is most likely the cause?

A.The BGP route has a higher AS path length than another route

B.The BGP route has been rejected by a policy

C.The BGP next-hop is unreachable

D.The BGP local preference is too high

AnswerC

For a BGP route to be active, its next-hop must be reachable via an existing route in the inet.0 routing table; if not, the BGP route is considered invalid and is placed in a hidden state. This is a fundamental BGP rule: the protocol relies on resolving next-hop addresses through IGP or static routes before installing the route. If the next-hop is unreachable, the route remains hidden in the BGP RIB and is not used for forwarding. This is the correct answer because it directly explains the hidden state.

Why this answer

In JUNOS, a BGP route is marked as 'hidden' in the routing table when the next-hop address is not reachable via any active route in the inet.0 table. This is a fundamental BGP path selection prerequisite: the next-hop must be resolvable (typically via an IGP or static route) for the route to be considered active and installed.

Exam trap

The trap here is that candidates often confuse 'hidden' with 'rejected by policy' or 'less preferred by AS path', but JUNOS specifically uses 'hidden' to indicate a next-hop unreachability issue, not a policy or selection problem.

How to eliminate wrong answers

Option A is wrong because a higher AS path length would make the route less preferred in BGP path selection, but it would not cause the route to be hidden; it would simply be outcompeted by a better path. Option B is wrong because if a BGP route is rejected by a policy, it typically does not appear in the routing table at all (or is marked as 'rejected'), not as 'hidden'. Option D is wrong because a high local preference makes a route more preferred, not hidden; local preference is a path attribute used in selection, not a condition that causes a route to be hidden.

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24

MCQmedium

A network engineer configures a static route to 10.0.0.0/8 with a preference of 20. An OSPF internal route to 10.0.0.0/8 has a default preference of 10. Which route will be active in the routing table?

A.Both routes, because they have different protocols.

B.Neither, because of a conflict.

C.The OSPF route, because of lower preference.

D.The static route, because it is manually configured.

AnswerC

Junos assigns each routing protocol a default preference, and the route with the lowest preference is chosen as the active route for a destination prefix. OSPF has a default preference of 10, which is lower than the static route's preference of 20. Therefore, the OSPF route is installed in the forwarding table and is the one used for traffic to 10.0.0.0/8.

Why this answer

In Junos, the active route in the routing table is determined by the lowest preference value. OSPF internal routes have a default preference of 10, while static routes have a default preference of 5, but here the static route is configured with a preference of 20. Since OSPF's preference (10) is lower than the static route's preference (20), the OSPF route is chosen as active.

Exam trap

The trap here is that candidates often assume static routes always take precedence over dynamic routes, but Junos uses a preference-based selection where a manually configured higher preference (20) makes the static route less preferred than OSPF's default (10).

How to eliminate wrong answers

Option A is wrong because Junos does not install multiple routes to the same prefix from different protocols unless they have equal preference; here preferences differ, so only the route with the lower preference is active. Option B is wrong because there is no conflict; the routing table selects the route with the lowest preference, and both routes are valid. Option D is wrong because manual configuration does not override the preference metric; the static route's higher preference (20) makes it less preferred than the OSPF route (10).

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25

MCQmedium

Your Juniper router is running OSPF with multiple neighbors. You have a prefix 10.10.10.0/24 that is being learned via OSPF from two different routers: Router A with metric 30 and Router B with metric 20. The OSPF route from Router B is active. You want to ensure that traffic to 10.10.10.0/24 uses the path through Router A instead, even though it has a higher metric. You cannot change the OSPF metric on Router A. Which action should you take?

A.Use a routing policy to increase the preference of the OSPF route from Router B.

B.Increase the metric on Router B for that prefix.

C.Use a routing policy to reject the OSPF route from Router A.

D.Configure a static route to 10.10.10.0/24 pointing to Router A.

AnswerA

Using a routing policy to increase the preference of the OSPF route from Router B makes that route less desirable in the Junos routing table. Since Junos selects the route with the lowest preference value, raising Router B's preference (say, from the default 10 to 15) leaves Router A's default OSPF route as the active path. This allows you to influence the active route selection centrally on the local router without changing OSPF metrics or filtering prefixes.

Why this answer

In JUNOS, route preference (administrative distance) determines which route is installed in the routing table when multiple protocols or sources provide the same prefix. By default, OSPF internal routes have a preference of 10. You can use a routing policy to increase the preference of the OSPF route from Router B (making it less preferred), which will cause the route from Router A (with its default preference of 10) to become active, even though its metric is higher.

This approach does not require changing the OSPF metric or removing the route from Router A.

Exam trap

The trap here is that candidates often confuse metric (cost) with preference (administrative distance) and think they must change the metric or reject routes, when in fact JUNOS allows preference manipulation via routing policies to influence route selection without altering the OSPF metric.

How to eliminate wrong answers

Option B is wrong because increasing the metric on Router B for that prefix would make the route from Router B even less attractive, but the goal is to prefer Router A; increasing Router B's metric would not help and might break other routing decisions. Option C is wrong because rejecting the OSPF route from Router A would remove the route entirely, but the question states the route from Router A is already not active; rejecting it would not make it active. Option D is wrong because configuring a static route to 10.10.10.0/24 pointing to Router A would install a static route with a default preference of 5, which is lower than OSPF's 10, making it active; however, this is not the best practice and does not leverage OSPF's dynamic capabilities, and the question asks for an action related to OSPF routes, not a static override.

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26

MCQeasy

A router has a directly connected route to 10.10.10.0/24 on interface ge-0/0/0.0, a static route to the same prefix with next-hop 192.168.1.1, and an OSPF route to the same prefix. Which route is active in the routing table?

A.The static route

B.No route is active due to multiple routes

C.The OSPF route

D.The directly connected route

AnswerD

Directly connected routes carry the lowest administrative distance in Junos, so they beat both the static route and the OSPF route to 10.10.10.0/24. Junos prefers the route with the lowest preference value when multiple protocols offer the same prefix, and the connected route's default preference of 0 wins.

Why this answer

In Junos, the routing table (inet.0) selects the active route based on the route preference (administrative distance). Directly connected routes have a default preference of 0, which is the lowest possible value, making them preferred over static routes (default preference 5) and OSPF routes (preference 10 for intra-area, 150 for external). Therefore, the directly connected route to 10.10.10.0/24 on ge-0/0/0.0 is active.

Exam trap

The trap here is that candidates familiar with Cisco IOS might assume static routes (AD 1) are preferred over OSPF (AD 110) but forget that directly connected routes (AD 0) always take precedence, or they might think multiple routes cause a tie or require load-balancing, which is incorrect for a single active route selection.

How to eliminate wrong answers

Option A is wrong because static routes have a default preference of 5 in Junos, which is higher than the directly connected route's preference of 0, so the static route is not selected. Option B is wrong because Junos does not deactivate all routes when multiple routes exist; it selects the route with the lowest preference, and only one route is active per prefix unless load-balancing is configured. Option C is wrong because OSPF routes have a preference of 10 (intra-area) or higher, which is greater than 0, so they are not preferred over the directly connected route.

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27

Multi-Selecteasy

Which TWO statements about route preferences in Junos are correct?

Select 2 answers

A.The preference of a route cannot be changed.

B.Direct routes have a default preference of 0.

C.OSPF internal routes have a default preference of 10.

D.Static routes have a default preference of 10.

E.BGP routes have a default preference of 200.

AnswersB, C

Direct routes, representing directly connected networks via active interfaces, are automatically assigned a default preference of 0 in Junos. This exceptionally low preference value ensures they are always the most preferred route source, taking precedence over all other route types like static, OSPF, or BGP routes. This mechanism is fundamental to Junos's routing logic, satisfying the question's requirement for a correct statement about route preferences.

Why this answer

In Junos, direct (connected) routes have a default route preference of 0, which is the highest possible preference, ensuring they are always preferred over other route types for directly attached networks. Option C is correct because OSPF internal routes (both intra-area and inter-area) have a default preference of 10 in Junos, which is lower than most other dynamic routing protocols, making OSPF routes more preferred by default.

Exam trap

The trap here is that candidates often confuse Junos default preference values with Cisco IOS administrative distance values, particularly for BGP (170 in Junos vs. 200 in Cisco) and static routes (5 in Junos vs. 1 in Cisco), leading them to select incorrect options based on Cisco knowledge.

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28

MCQeasy

You are managing a small enterprise network with one Juniper router and two switches. The router connects to an ISP via ge-0/0/0 and to the internal network via ge-0/0/1. The internal network uses the 192.168.1.0/24 subnet. You need to configure a default route on the router to send all Internet-bound traffic to the ISP gateway at 203.0.113.1. You also want to ensure that internal hosts can reach the Internet. After configuring the default route, you test connectivity from a host on the internal network to an external website, but the ping fails. You verify that the host has an IP address of 192.168.1.100/24 and a default gateway of 192.168.1.1 (the router's internal interface). On the router, you run 'show route 0.0.0.0/0' and see the default route active. You also run 'ping 203.0.113.1' from the router and it succeeds. However, pinging from the host to the ISP gateway fails. What is the most likely cause?

A.DNS resolution is failing on the host.

B.The host's default gateway is incorrectly configured.

C.The default route is not active on the router.

D.Proxy ARP is not enabled on the router's internal interface.

AnswerB

This is the most likely cause. The host's default gateway is incorrectly configured, preventing it from sending packets to the router. Even though the stem says it is set to 192.168.1.1, this could be a misinterpretation or the host may have a different gateway configured at the OS level.

Why this answer

The host's default gateway is configured as 192.168.1.1, which is the router's internal interface. However, if the host's gateway is incorrectly set (e.g., to a different IP or a non-existent router), it cannot send packets to the router. The router's default route and ping to the ISP gateway succeed from the router itself, indicating the router's configuration is correct.

The failure from the host points to an issue at the host's network configuration, most likely the default gateway setting. Other possibilities include NAT or return route issues, but these are not listed as options. Proxy ARP is not required for directly connected hosts and is not the most likely cause.

Exam trap

Candidates often focus on router-side issues like default routes or Proxy ARP, but the host's gateway configuration is a common point of failure. Always verify the host's network settings first when host-to-external connectivity fails but router connectivity succeeds.

How to eliminate wrong answers

Option A is wrong because DNS resolution is not required for a ping to an IP address; the ping command uses the IP directly, so DNS failure would not cause the ping to fail. Option B is wrong because the host's default gateway is correctly set to 192.168.1.1, which is the router's internal interface IP; this is verified by the host having an IP of 192.168.1.100/24 and the router's ge-0/0/1 being on the same subnet. Option C is wrong because the 'show route 0.0.0.0/0' command confirmed the default route is active on the router, and the ping from the router to 203.0.113.1 succeeded, proving the route is functional.

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29

Multi-Selecthard

Which TWO factors are directly used when comparing route preferences in JunOS? (Choose two.)

Select 2 answers

A.Next-hop reachability

B.Number of hops

C.Metric (or cost)

D.Prefix length

E.Preference value

AnswersC, E

Metric (or cost) is the second key factor used in route comparison, applied only after the route preference has been considered. Within the same protocol, the route with the lower metric is preferred—for example, OSPF uses cost, IS-IS uses metric, and RIP uses hop count. Metrics are not comparable across different protocols, which is precisely why preference is checked first: once the preferred protocol is chosen, its metric decides among equal-preference routes. A lower metric value means a more preferred route, all else being equal.

Why this answer

In Junos, route preference (also called administrative distance) is the primary tie-breaker used to compare routes from different protocols, so option E (Preference value) is directly used — lower preference wins, e.g., direct=0, static=5, OSPF internal=10, RIP=100. When two routes come from the same protocol, the protocol's metric/cost is compared, so option C (Metric or cost) is also directly used, e.g., OSPF cost or RIP hop count. Option A (Next-hop reachability) is a validity condition for installing a route, not a comparison factor between competing routes.

Option B (Number of hops) is only a metric within protocols like RIP, not a universal Junos comparison factor. Option D (Prefix length) is used for longest-match forwarding lookups in the forwarding table, not for route preference comparison in the routing table.

Exam trap

The trap here is that candidates often confuse route preference (administrative distance) with metric or prefix length, but JunOS uses preference first, then metric, while prefix length is only relevant for longest-match forwarding, not for route preference comparison.

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30

MCQhard

A static route to 10.0.0.0/8 has next-hop 192.168.1.1. The route is not installed in the routing table. Which condition must be met for the route to become active?

A.The static route must have a lower preference than any dynamic route to the same prefix.

B.The next-hop must have an ARP entry in the ARP table.

C.The next-hop 192.168.1.1 must be reachable via an active route (e.g., a direct or OSPF route).

D.The metric of the static route must be lower than that of any other route to the same prefix.

AnswerC

A static route with an indirect next-hop is installed in the Junos routing table only after the next-hop address is recursively resolved via a routing table lookup. In this case, 192.168.1.1 must be matched by an active route — such as a directly connected subnet, an OSPF route, or another static route — otherwise the static route to 10.0.0.0/8 is marked as unresolved and is not placed in the forwarding table. This resolution is required regardless of the static route's preference or metric. If the active route to the next-hop is removed, the static route is immediately hidden from the active route table.

Why this answer

For a static route to be installed in the Junos routing table, its next-hop must be reachable via an active route in the routing table. This is because Junos performs recursive next-hop resolution: it looks up the next-hop IP address (192.168.1.1) in the routing table and requires a valid, active route (e.g., a directly connected or OSPF-learned route) to that address. Without this, the static route remains hidden and is not installed.

Exam trap

The trap here is that candidates often confuse the requirement for the next-hop to be reachable (a routing table condition) with Layer 2 resolution (ARP), leading them to incorrectly select Option B, but ARP is only used after the route is installed and the next-hop is determined to be reachable.

How to eliminate wrong answers

Option A is wrong because preference (administrative distance) only determines which route is selected among multiple routes to the same prefix that are already active; it does not affect whether a static route becomes active in the first place. Option B is wrong because an ARP entry is a Layer 2 resolution mechanism that occurs after the route is installed and the next-hop is reachable; the route will not become active solely because an ARP entry exists. Option D is wrong because metric is not used for static route selection in Junos; static routes have no metric, and route selection is based on preference, not metric.

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31

Multi-Selecteasy

Which two factors does Junos use to select the best route when multiple routes to the same prefix exist? (Choose two.)

Select 2 answers

A.Route preference

B.Next-hop type

C.Number of hops

D.Metric

E.Route age

AnswersA, D

Route preference is the first and primary criterion Junos uses to choose the best route to a destination. Each routing protocol is assigned a default preference value (e.g., 10 for OSPF, 20 for static, 170 for BGP), and the route with the lowest preference wins. You can modify these values with routing policy or by setting a custom preference, but the comparison always happens before any metric is examined.

Why this answer

Junos route selection first compares route preference (administrative distance), so option A is correct because the route with the lower preference value (for example, direct 0, static 5, OSPF 10, RIP 100, BGP 170) wins before any protocol-specific metric is considered. If routes have equal preference, Junos then compares the metric, so option D is correct because the lower metric is preferred within the same protocol or routing table. Options B, C, and E are not the two primary Junos best-route selection factors: next-hop type, hop count, and route age are not used as the general tie-breakers in the Junos route selection algorithm.

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32

MCQhard

Two routers running IBGP with full mesh have a routing loop for prefix 10.1.1.0/24. Both routers have an IBGP route (preference 170) for the prefix with next-hop 10.2.2.2, and an OSPF route (preference 10) for the same prefix. The OSPF next-hop on each router points to the other router's loopback interface. Which action should be taken to stop the loop while preserving BGP route advertisement?

A.Increase the OSPF preference for 10.1.1.0/24 to 175

B.Add a static route for 10.1.1.0/24 with next-hop 10.2.2.2

C.Configure 'set protocol bgp group internal-mesh local-address 10.2.2.2' to set next-hop to self

D.Use route reflection to break the loop

AnswerA

In Junos, route preference is the first criterion in the route selection process. OSPF internal routes default to a preference of 10, while iBGP routes default to 170, so the router installs the OSPF route even if the BGP route has a better path out of the loop. By raising OSPF preference for 10.1.1.0/24 to 175, you make OSPF less desirable than BGP (170), allowing the iBGP route to become active and use a next hop that exits the loop. This targeted override of the default preference for a specific prefix resolves the loop without affecting other routes.

Why this answer

Increasing the OSPF preference for 10.1.1.0/24 to 175 makes the IBGP route (preference 170) more preferred than the OSPF route. This breaks the routing loop where each router's OSPF route points to the other's loopback, while preserving the IBGP route advertisement. The loop occurs because both routers prefer the OSPF route (preference 10) over IBGP (preference 170), causing traffic to bounce between them.

Exam trap

The trap here is that candidates may think the loop is caused by BGP next-hop behavior or session configuration, rather than recognizing it as a route preference issue where OSPF's lower preference overrides IBGP, leading to a forwarding loop between the two routers.

How to eliminate wrong answers

Option B is wrong because adding a static route for 10.1.1.0/24 with next-hop 10.2.2.2 would create a static route with default preference 5, which is more preferred than both OSPF and IBGP, but it does not address the loop caused by OSPF routes pointing to each other's loopbacks; it could also interfere with BGP route advertisement. Option C is wrong because configuring 'set protocol bgp group internal-mesh local-address 10.2.2.2' sets the local address for BGP sessions but does not change the next-hop for the IBGP route; the next-hop remains 10.2.2.2, and this does not resolve the OSPF route preference issue. Option D is wrong because route reflection is a scalability feature for IBGP that reduces the number of sessions, but it does not affect route preference or break the loop caused by OSPF routes being preferred over IBGP.

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33

MCQhard

During a routing table lookup, a packet matches both a static route and an OSPF route to the same destination. Which route will be installed in the forwarding table?

A.Both routes, if they are equal-cost.

B.The route with the higher preference value.

C.The OSPF route, because OSPF is a dynamic routing protocol.

D.The static route, because it has a lower preference value.

AnswerD

Junos routes are selected by comparing the preference values from different protocols, and the route with the lowest preference is installed as active in the forwarding table. Static routes have a default preference of 5, while OSPF internal routes use 10, so the static route is chosen. This lower preference value reflects that static routes are manually configured and therefore considered the most reliable and predictable source for that destination.

Why this answer

In Junos, the route with the lowest preference value is installed in the forwarding table. Static routes have a default preference of 5, while OSPF internal routes have a default preference of 10. Therefore, the static route is preferred and installed.

Exam trap

The trap here is that candidates often assume dynamic protocols like OSPF are always preferred over static routes, but Junos uses preference (administrative distance) where static routes have a lower default value than OSPF, making them more preferred.

How to eliminate wrong answers

Option A is wrong because Junos installs only the single best route (lowest preference) into the forwarding table; equal-cost multipath only applies when routes have the same preference and metric, which is not the case here. Option B is wrong because a higher preference value indicates a less preferred route; the route with the lower preference value is chosen. Option C is wrong because the decision is based on administrative distance (preference), not on whether the protocol is dynamic or static; OSPF has a higher preference (10) than a static route (5), so the static route wins.

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34

MCQmedium

Your company recently acquired a small office that uses a Juniper MX router to connect to two ISPs for redundancy. The router has two uplinks: xe-0/0/0 to ISP-A (next-hop 10.0.0.1) and xe-0/0/1 to ISP-B (next-hop 10.0.1.1). The router receives a full BGP table from both ISPs. You want to prefer ISP-A for most traffic, but use ISP-B as a backup. You have configured BGP with local-preference 200 on routes from ISP-A and local-preference 100 on routes from ISP-B. After committing, you check the routing table and see that for some destinations, the route from ISP-B is active despite having lower local-preference. What is the most likely reason?

A.The local-preference is not applied to routes that are learned via eBGP; it only works for iBGP.

B.The router is not receiving the ISP-A routes for those specific prefixes; perhaps ISP-A's BGP session is missing or the prefix is not advertised.

C.The IGP metric to the next-hop from ISP-B is lower, causing the route to be preferred.

D.The MED value from ISP-A is higher than from ISP-B, overriding the local-preference.

AnswerB

BGP best-path selection can only evaluate routes that are actually present in the BGP table. If the prefixes are not being received from ISP-A—because the eBGP session is down, the neighbor is not advertising them, or inbound filtering is discarding them—the router has only the ISP-B routes to consider, so the local-preference setting for ISP-A is irrelevant. The route from ISP-B then wins by default, exactly matching the observed symptoms.

Why this answer

The correct answer is B: the router is likely not receiving the ISP-A routes for those specific prefixes, perhaps because ISP-A's BGP session is missing or the prefix is not advertised. Local-preference is evaluated before MED and IGP metric in the BGP best-path selection process, so if a route from ISP-A with local-preference 200 existed for those destinations, it would be preferred over the ISP-B route with local-preference 100. If ISP-A simply isn't advertising those prefixes (or the session is down), no ISP-A route exists to compare, so the ISP-B route becomes active.

Option A is false because local-preference is a well-known discretionary attribute that is commonly set on eBGP-learned routes via inbound policy. Option C is wrong because IGP metric is only considered after local-preference and MED, so it cannot override a higher local-preference. Option D is wrong because MED is compared after local-preference, so a higher MED from ISP-A would not cause the lower-local-preference ISP-B route to win.

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35

MCQmedium

You are configuring a Juniper MX router to act as a BGP route reflector for your ISP network. The router has several iBGP peers, including clients and non-clients. You have configured the route-reflector-cluster-id and set the clients. After the configuration, you notice that some prefixes are not being reflected to a specific client router. The client has a valid BGP session to the route reflector and can see other prefixes. You check the BGP routing table on the route reflector and see that the missing prefixes are present but have the 'non-routable' flag. The route reflector's BGP table shows the prefix with a next-hop that is not reachable via an IGP route. What is the most likely cause?

A.The next-hop for the missing prefixes is not reachable via the IGP on the route reflector; the route reflector needs a route to the next-hop to advertise the prefix.

B.The route-reflector-cluster-id is set incorrectly, causing the route reflector to drop the route to prevent loops.

C.The ORIGINATOR_ID attribute from a previous route reflector is causing the route to be suppressed.

D.The route reflector is using the next-hop-self option and cannot resolve its own IP as a next-hop.

AnswerA

For a BGP route to be eligible for advertisement, the router must be able to resolve the next-hop through an active route in its routing table. On a route reflector, this means the IGP (such as OSPF or IS-IS) must have a route to the next-hop IP of the reflected prefix. If that route is missing, the prefix is flagged as non-routable and is not advertised to clients, exactly as observed in the question.

Why this answer

The correct answer is A: the next-hop for the missing prefixes is not reachable via the IGP on the route reflector, and the route reflector needs a route to the next-hop to advertise the prefix. In Junos, a BGP route is marked non-routable (hidden) when the next-hop cannot be resolved in the inet.0 routing table, and such unresolved routes are not eligible for advertisement to BGP peers, including route-reflector clients. Since the session is up and other prefixes are received, the issue is next-hop resolution rather than session or reflection configuration.

Option B is wrong because an incorrect cluster ID would cause loop-prevention behavior (such as rejecting routes with its own cluster ID), not a non-routable flag from an unresolved next-hop. Option C is wrong because ORIGINATOR_ID suppression would drop routes originated by the same router, not mark them non-routable. Option D is wrong because next-hop-self changes the advertised next-hop to the route reflector's own address, which is locally reachable and would not cause this non-routable condition.

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36

MCQeasy

Which Junos command displays the route to a specific IP address, including the active route and any backup routes?

A.show route 192.168.1.1

B.show route protocol

C.show route active

D.show route table

AnswerA

The `show route 192.168.1.1` command is the precise Junos CLI command to query the routing table for a specific destination IP address. It displays all routes in the inet.0 table (and other tables if applicable) that match that prefix, including the next-hop, protocol, and preference. This is the standard way to verify reachability and determine which path will be used for forwarding to that address.

Why this answer

The 'show route 192.168.1.1' command in Junos displays all routes in the routing table that match the specified destination, including the active route (marked with '>') and any backup routes (marked with a space). This command provides a comprehensive view of the forwarding table entries for that prefix, which is essential for understanding both primary and failover paths.

Exam trap

The trap here is that candidates familiar with Cisco IOS might expect 'show ip route <ip>' to show only the best route, but in Junos, the same command reveals all routes, including backups, which can lead to confusion if one assumes only the active route is displayed.

How to eliminate wrong answers

Option B is wrong because 'show route protocol' filters routes by a specific routing protocol (e.g., static, OSPF, BGP) and does not show routes to a specific IP address with active and backup routes. Option C is wrong because 'show route active' displays only the active routes in the routing table, omitting any backup or inactive routes. Option D is wrong because 'show route table' displays the entire routing table for a specific table (e.g., inet.0) without filtering to a particular destination, so it does not isolate the route to 192.168.1.1 or highlight active versus backup routes.

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37

MCQeasy

A network engineer configures a static route to a remote network. They want the route to be automatically removed from the routing table if the directly connected interface used to reach the next hop fails. Which configuration approach should be used?

A.Configure a higher metric on the static route.

B.Configure a preference of 0 on the static route.

C.Configure the next-hop as an IP address.

D.Configure the next-hop as the interface name.

AnswerD

In Junos, specifying an interface name as the next-hop creates an interface-dependent static route that is installed only when that interface is present and operational. When the interface goes down, the route is automatically withdrawn from both the routing and forwarding tables, allowing immediate failover to any backup route. This is exactly the behavior needed to remove the route without relying on ARP timeout or reachability checks.

Why this answer

Configuring the next-hop as an interface name (e.g., ge-0/0/0) creates a static route that is automatically removed from the routing table when that interface goes down. This is due to the route being 'qualified' by the interface's operational state; if the interface fails, the route is withdrawn. In contrast, using an IP address as the next-hop does not tie the route to the interface's state, so the route remains even if the interface fails, as long as the next-hop is reachable via another path.

Exam trap

The trap here is that Cisco engineers often assume that specifying a next-hop IP address is the only valid way to configure a static route, but in Junos, using the interface name directly ties the route to the interface's state, which is the key to automatic removal upon interface failure.

How to eliminate wrong answers

Option A is wrong because configuring a higher metric on a static route does not cause it to be removed when an interface fails; metric (or cost) is used for route selection among multiple routes to the same destination, not for interface-based withdrawal. Option B is wrong because setting a preference of 0 makes the static route the most preferred route (lowest preference value), but it does not tie the route to the interface's operational state; the route remains even if the interface fails. Option C is wrong because configuring the next-hop as an IP address creates a static route that is not automatically removed when the directly connected interface fails; the route persists in the routing table unless the next-hop becomes unreachable via any interface, which may not happen if an alternate path exists.

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38

Multi-Selecthard

Which three characteristics are true for OSPF? (Choose three.)

Select 3 answers

A.Uses the Bellman-Ford algorithm

B.Supports VLSM (Variable Length Subnet Masks)

C.Uses cost as the metric

D.Uses the SPF (Shortest Path First) algorithm

E.Is classful and does not support VLSM

AnswersB, C, D

OSPF is a classless routing protocol, meaning it carries the subnet mask in its routing updates, enabling VLSM and CIDR. This allows different interfaces on the same network to use different-length subnet masks, optimizing address space utilization. In contrast, classful protocols like RIPv1 cannot advertise subnet masks and thus cannot support VLSM, whereas OSPF's type-1 and type-3 LSAs explicitly include the mask.

Why this answer

OSPF is a link-state routing protocol that supports VLSM (Variable Length Subnet Masks), so option B is correct because it carries subnet mask information in its LSAs, allowing classless, hierarchical addressing. Option C is correct because OSPF's default metric is cost, which is derived from interface bandwidth (reference bandwidth divided by interface bandwidth). Option D is correct because OSPF uses the Dijkstra Shortest Path First (SPF) algorithm to compute the loop-free shortest-path tree from the link-state database.

Option A is incorrect because the Bellman-Ford algorithm is used by distance-vector protocols such as RIP, not OSPF. Option E is incorrect because OSPF is classless and explicitly supports VLSM, contradicting the statement.

Exam trap

The trap here is that candidates often confuse OSPF's metric (cost) with hop count or bandwidth, or mistakenly think OSPF is classful like RIPv1, but OSPF is inherently classless and uses a link-state algorithm, not Bellman-Ford.

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39

MCQhard

Refer to the exhibit. The route for 192.168.0.0/16 is hidden. What is the most likely reason?

A.The BGP next-hop is unreachable

B.The route has a lower local preference

C.The route has a longer AS path

D.The route has a higher MED value

AnswerA

In Junos, a BGP route is considered 'hidden' when it cannot be installed into the inet.0 routing table because its BGP next-hop address is not resolvable by an active IPv4 or IPv6 route. The route remains in the BGP database (Adj-RIB-In) but is excluded from forwarding and from best-path selection. Use 'show route protocol bgp hidden' to display such routes; as soon as next-hop reachability is restored, the route becomes visible and active.

Why this answer

In JUNOS, a BGP route is hidden when the next-hop address is not reachable via any active route in the routing table. The router cannot install the route into the forwarding table because it lacks a valid path to the next-hop, causing the route to be marked as hidden. This is a common issue when the next-hop is not covered by a directly connected or static route, or when the IGP route to the next-hop is missing.

Exam trap

The trap here is that candidates often confuse route selection attributes (like local preference, AS path, MED) with route installation conditions, assuming a less preferred attribute hides the route, when in fact only next-hop unreachability or policy-based rejection can cause a route to be hidden in JUNOS.

How to eliminate wrong answers

Option B is wrong because local preference is a BGP path attribute used for route selection within an AS, but it does not cause a route to be hidden; a lower local preference would simply make the route less preferred but still active. Option C is wrong because a longer AS path affects route selection by making the route less preferred, but it does not hide the route; the route remains visible in the routing table. Option D is wrong because a higher MED value influences route selection between multiple paths to the same prefix, but it does not cause a route to be hidden; the route would still be active if the next-hop is reachable.

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40

MCQmedium

An organization has two ISPs and wants to load-balance traffic equally across both links for all outbound traffic. Which routing configuration approach should be used?

A.Configure two static default routes with different metric values.

B.Configure policy-based routing to match all traffic and forward to both ISPs.

C.Configure two static default routes with equal metric values and enable ECMP.

D.Establish BGP sessions with both ISPs and rely on BGP path selection.

AnswerC

In Junos, two static default routes with equal metrics have the same preference and are both installed in the routing table as equal-cost paths. To actually balance traffic, you must enable ECMP, typically by configuring 'load-balance per-packet' in the forwarding options or a policy statement. This allows Junos to distribute flows across both ISPs while maintaining per-flow consistency, which is essential for TCP sessions.

Why this answer

Configuring two static default routes with equal metric values and enabling Equal-Cost Multi-Path (ECMP) allows the Juniper device to load-balance outbound traffic equally across both ISP links. ECMP uses per-flow or per-packet load balancing based on the hash of source/destination IP addresses and ports, ensuring traffic is distributed evenly without relying on dynamic routing protocols.

Exam trap

The trap here is that candidates often confuse metric (cost) with preference (administrative distance) in Junos, assuming that different metric values still allow load balancing, whereas Junos requires equal metric values for ECMP to activate.

How to eliminate wrong answers

Option A is wrong because configuring two static default routes with different metric values results in only the route with the lower metric being active in the routing table, providing failover but not load balancing. Option B is wrong because policy-based routing (PBR) can forward traffic based on match criteria, but it does not inherently load-balance equally across two links without additional configuration like filter-based forwarding and per-packet load balancing, which is not the standard approach for simple equal load sharing. Option D is wrong because establishing BGP sessions with both ISPs and relying on BGP path selection does not guarantee equal load balancing; BGP selects only the best path based on attributes like local preference and AS path length, and additional configuration (e.g., multipath) is required to enable ECMP for BGP routes.

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41

MCQmedium

Refer to the exhibit. The router has a default static route and a static route to 10.0.0.0/24. An engineer updates the next-hop for the default route from 192.168.1.1 to 192.168.1.2. Which command should the engineer use to verify that the change is active?

A.show route 192.168.1.2

B.ping 192.168.1.2

C.show route 0.0.0.0/0

D.show route protocol static

AnswerC

The `show route 0.0.0.0/0` command directly queries the IPv4 default prefix in the inet.0 routing table, and Junos will display the active default route along with its next-hop IP address, outgoing interface, and route preference (administrative distance). This is the definitive way to confirm that a default static route is installed and to see exactly where traffic for unmatched destinations will be forwarded. If multiple default routes exist, this command shows only the active one—the one selected by lowest preference—while hidden routes are flagged or omitted. This focused lookup is the most precise verification of the default route itself.

Why this answer

The command 'show route 0.0.0.0/0' displays the routing table entry for the default route, including its next-hop address. After changing the next-hop from 192.168.1.1 to 192.168.1.2, this command confirms the active route has the updated next-hop. It directly verifies the specific prefix that was modified.

Exam trap

The trap here is that candidates often choose 'show route protocol static' thinking it shows all static routes, but they fail to realize it does not isolate the specific prefix changed, and the engineer needs to confirm the next-hop for 0.0.0.0/0, not just any static route.

How to eliminate wrong answers

Option A is wrong because 'show route 192.168.1.2' shows routes to that specific host address, not the default route; it would only confirm reachability to the next-hop, not the change to the default route. Option B is wrong because 'ping 192.168.1.2' tests IP connectivity to the next-hop address but does not verify that the default route in the routing table has been updated; the ping could succeed even if the route change failed. Option D is wrong because 'show route protocol static' displays all static routes, including both the default route and the route to 10.0.0.0/24, but it does not focus on the specific prefix 0.0.0.0/0; the engineer needs to confirm the change for that exact prefix, not all static routes.

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42

MCQhard

Refer to the exhibit. Which route is active for the 192.168.1.0/24 prefix?

A.Both routes are active.

B.The static route because it has a lower preference.

C.Neither route is active.

D.The OSPF route because it is marked with an asterisk.

AnswerD

The asterisk in the routing table marks the active route installed in the forwarding table. Junos selects the OSPF route for 192.168.1.0/24 because it has the lowest preference value compared with competing protocols, satisfying the stem's requirement to identify which route is actually active.

Why this answer

The correct answer is D: the OSPF route is active because it is marked with an asterisk, which in this routing table indicates the route currently installed in the forwarding table for 192.168.1.0/24. When multiple routing sources offer the same prefix, the device selects one best route based on administrative distance or preference, and only that selected route is flagged as active. The static route, despite being present in the table, is not the active entry for this prefix in the exhibit.

Options A, B, and C are incorrect because only one route is active, the static route is not the selected one, and at least one route is active.

Exam trap

The trap is that candidates often assume a static route always wins over OSPF due to its lower preference, but they overlook that the asterisk in JUNOS output directly indicates the active route. Additionally, a static route may be inactive despite lower preference if its next-hop is unreachable or if it was configured with a custom preference higher than OSPF's default.

How to eliminate wrong answers

Option A is wrong because both routes cannot be active for the same prefix; JUNOS selects only one active route based on the lowest preference value. Option B is wrong because although a static route has a lower preference (5) than OSPF (10), the exhibit shows the OSPF route with an asterisk, indicating it is the active route; this means the static route is not active despite its lower preference, possibly due to the static route being configured with a next-hop that is unreachable or the route being inactive for another reason. Option C is wrong because the OSPF route is marked with an asterisk, which explicitly indicates it is active in the routing table.

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43

MCQeasy

Refer to the exhibit. What does the 'user' type indicate about the route?

A.The route is from the kernel.

B.The route was manually configured.

C.The route is a default route generated by the router.

D.The route was learned from a routing protocol.

AnswerB

The 'user' route type in Junos specifically indicates that the route was manually configured by an administrator, typically as a static route. When you see this type in the routing table, it confirms that the route was entered via configuration commands and not dynamically learned or automatically generated. This is a quick way to distinguish static routes from protocol-learned or kernel-derived routes in the routing table.

Why this answer

In Junos, the 'user' type in a route table indicates that the route was manually configured, typically via a static route statement under the 'routing-options' hierarchy. This distinguishes it from routes learned dynamically through routing protocols or derived from the kernel's interface addresses.

Exam trap

The trap here is that candidates often confuse 'user' with 'kernel' or 'direct' routes, mistakenly thinking any route not learned from a protocol must be kernel-generated, but Junos explicitly labels manually configured static routes as 'user' to differentiate them from kernel-derived interface routes.

How to eliminate wrong answers

Option A is wrong because the 'user' type does not indicate a kernel-derived route; kernel routes are typically marked with the 'kernel' type, which includes directly connected and local interface routes. Option C is wrong because a default route generated by the router (e.g., via a dynamic routing protocol or default-route advertisement) would show a protocol type like 'static', 'ospf', or 'bgp', not 'user'. Option D is wrong because routes learned from a routing protocol (e.g., OSPF, BGP, IS-IS) are marked with the respective protocol type (e.g., 'ospf', 'bgp'), not 'user'.

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44

MCQhard

Refer to the exhibit. What is the most likely cause of this BGP route being hidden?

A.The route has a higher preference than another route.

B.The BGP session to 10.0.0.2 is down.

C.The prefix 10.1.1.0/24 is filtered by an import policy.

D.The next-hop 192.168.100.1 is not reachable via any active route.

AnswerD

An unreachable next-hop prevents BGP from validating the path, so the route stays hidden rather than becoming active. Junos requires the next-hop to resolve through an active route in the routing table; with no such route, the prefix fails next-hop resolution and is withheld from the forwarding table.

Why this answer

In JUNOS, a BGP route is hidden when the next-hop address is not reachable via any active route in the routing table. The show route protocol bgp command displays the route as hidden if the next-hop 192.168.100.1 is not resolvable, because BGP requires a valid IGP or static route to the next-hop for the route to be considered active and installed in the forwarding table.

Exam trap

The trap here is that candidates often confuse a hidden route with a route that is filtered by policy or has a higher preference, but JUNOS specifically uses the 'hidden' flag to indicate next-hop unreachability, not policy rejection or preference comparison.

How to eliminate wrong answers

Option A is wrong because a higher preference (lower administrative distance) would make the route more preferred, not hidden; hidden routes are not a result of preference comparison but of next-hop unreachability or policy filtering. Option B is wrong because if the BGP session to 10.0.0.2 were down, the route would not appear in the routing table at all, rather than being marked as hidden. Option C is wrong because if the prefix 10.1.1.0/24 were filtered by an import policy, the route would not be present in the routing table (neither active nor hidden), whereas a hidden route is still present but not usable due to next-hop issues.

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45

MCQhard

A router has two ISIS adjacencies to the same router, both with equal metrics. The router installs both routes in the routing table and performs load balancing. The network team wants to verify that both next-hops are being used for a particular destination. Which command provides this information?

A.`show route 10.0.0.0/24 extensive`

B.`show route forwarding-table destination 10.0.0.0/24`

C.`show route protocol isis`

D.`show route 10.0.0.0/24 detail`

AnswerB

`show route forwarding-table destination 10.0.0.0/24` is the authoritative command for verifying actual forwarding behavior. It displays the forwarding-table entry, where the next-hop has been resolved to a specific interface and IP address (e.g., via ARP or neighbor discovery), and it explicitly shows whether multiple next-hops are installed with equal weights for load balancing. This is the only command in the set that shows the PFE's forwarding state, so it directly answers which next-hops are used when forwarding packets to 10.0.0.0/24.

Why this answer

The `show route forwarding-table destination 10.0.0.0/24` command displays the actual forwarding entries in the Packet Forwarding Engine (PFE), including all next-hops used for load balancing. Unlike the routing table, the forwarding table shows which next-hops are actively installed and used for forwarding traffic, making it the definitive command to verify equal-cost multipath (ECMP) usage.

Exam trap

The trap here is that candidates assume `show route` commands (like `detail` or `extensive`) confirm actual forwarding behavior, but in Junos, only the forwarding table reveals which next-hops are truly used for packet forwarding, especially under ECMP.

How to eliminate wrong answers

Option A is wrong because `show route 10.0.0.0/24 extensive` shows detailed routing table information, including multiple next-hops, but it does not confirm which next-hops are actually used in the forwarding plane; it only shows the routing table state. Option C is wrong because `show route protocol isis` filters routes by protocol but does not provide per-destination next-hop usage or forwarding table details. Option D is wrong because `show route 10.0.0.0/24 detail` shows routing table details for a specific prefix, including multiple next-hops, but like option A, it does not verify the forwarding table's active next-hops for load balancing.

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46

MCQeasy

A network administrator configures a static route on a Juniper device: `set routing-options static route 192.168.100.0/24 next-hop 10.0.0.1`. The administrator verifies the route is present in the routing table but notices it is not active. What is the most likely cause?

A.The route is not committed.

B.The next-hop address 10.0.0.1 is not reachable.

C.The preference of the static route is higher than 15.

D.The destination prefix is already learned via OSPF with a lower metric.

AnswerB

Junos installs a static route only when its next-hop resolves via a reachable interface. If 10.0.0.1 is unreachable, the route stays inactive in the routing table, satisfying the stem's condition of a present but non-active route.

Why this answer

A static route becomes active only if the next-hop address is reachable via a directly connected or active route in the routing table. Since the administrator verified the route is present but not active, the most likely cause is that the next-hop 10.0.0.1 is not reachable (e.g., no ARP resolution or no interface with that subnet). Junos marks such routes as hidden or inactive until the next hop is reachable.

Exam trap

The trap here is that candidates often assume a static route is always active once configured and committed, overlooking Junos's requirement that the next-hop must be reachable via an active directly connected route for the route to be installed as active.

How to eliminate wrong answers

Option A is wrong because the route is already present in the routing table, which means it has been committed; an uncommitted route would not appear at all. Option B is the correct answer as explained. Option C is wrong because the default preference for static routes in Junos is 5, which is lower than 15, and a higher preference (worse) would not prevent activation—it would only affect route selection among multiple routes to the same prefix.

Option D is wrong because OSPF routes have a default preference of 10 (internal) or 150 (external), and a static route with preference 5 would be preferred over OSPF; moreover, the question states the route is not active, not that it is not preferred.

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47

MCQhard

An engineer is configuring multiple static routes to the same destination for redundancy. The primary link uses 192.168.1.1 and the backup uses 192.168.2.1. They want the backup to be used only when the primary next-hop is unreachable. Which configuration is correct?

A.Configure the primary with a lower preference and the backup with a higher preference.

B.Configure the primary with a higher preference and the backup with a lower preference.

C.Configure two static routes with equal preferences; the active route will be chosen based on next-hop IP.

D.Configure the routes with the same preference but use a policy to set metric.

AnswerA

In Junos, route preference acts as an administrative distance, and a numerically lower value is always preferred. Assigning the primary static route a lower preference ensures it is installed in the routing and forwarding tables, while the higher-preference backup remains inactive. If the primary's next-hop becomes unreachable, the primary route is withdrawn and the backup is automatically promoted, providing the required failover behavior.

Why this answer

In JUNOS, a lower preference value indicates a more preferred route. By setting the primary next-hop (192.168.1.1) with a lower preference (e.g., 5) and the backup next-hop (192.168.2.1) with a higher preference (e.g., 10), the primary route is installed in the routing table. If the primary next-hop becomes unreachable, the route is withdrawn, and the backup route with the higher preference is then installed, providing redundancy.

Exam trap

Candidates often confuse preference with metric, thinking that equal preferences with a policy can achieve failover, but JUNOS does not use metric for static route selection. With equal preferences, both static routes are installed and load-balanced, so the backup is used even when the primary is reachable. To ensure the backup is only used when the primary fails, configure the primary with a lower preference and the backup with a higher preference.

How to eliminate wrong answers

Option B is wrong because configuring the primary with a higher preference and the backup with a lower preference would cause the backup to be preferred over the primary, defeating the purpose of having a primary link. Option C is wrong because two static routes with equal preferences to the same destination will result in both being installed in the routing table, but only one will be active based on the next-hop IP (the lower IP wins), which does not provide failover based on reachability; if the active next-hop fails, the route is not automatically switched to the other next-hop because both routes are still present. Option D is wrong because in JUNOS, static routes do not have a metric field; preference is the primary tiebreaker, and using a policy to set metric is not applicable for static route selection.

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48

MCQmedium

An administrator wants to drop traffic destined to the 10.10.10.0/24 network without sending an ICMP unreachable message back to the source. Which static route option should be used?

A.reject

B.discard

C.next-table

D.resolve

AnswerB

The discard next-hop type installs a route that silently drops the packet without sending any ICMP response. The forwarding engine discards the traffic in the data plane, so it consumes no control-plane CPU for error messages. This is the standard Junos way to implement a blackhole route for an unreachable prefix, matching the administrator's intent to drop traffic.

Why this answer

The 'discard' static route option silently drops traffic destined to the 10.10.10.0/24 network without generating any ICMP unreachable message. This is in contrast to the 'reject' option, which drops traffic but sends an ICMP unreachable back to the source. The 'discard' route is ideal for blackholing unwanted traffic while avoiding unnecessary network feedback.

Exam trap

The trap here is that candidates often confuse 'reject' with 'discard' because both drop traffic, but they fail to remember that 'reject' sends an ICMP unreachable message, which the question explicitly prohibits.

How to eliminate wrong answers

Option A is wrong because 'reject' drops traffic but sends an ICMP Destination Unreachable message to the source, which the administrator explicitly wants to avoid. Option C is wrong because 'next-table' is used to direct traffic to another routing table for further lookup, not to drop traffic. Option D is wrong because 'resolve' is used to require that the next-hop of a static route be reachable via another route; it does not drop traffic.

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49

MCQmedium

An administrator suspects that routing protocol updates are being sent to an incorrect next-hop. Which command can be used to capture and analyze the routing protocol packets on an interface?

A.show log messages | match ospf

B.show route forwarding-table

C.show ospf neighbor detail

D.monitor traffic interface ge-0/0/0.0

AnswerD

This command triggers a live packet capture on the specified interface, displaying all traffic that enters or exits the interface in real time, much like tcpdump. It can be narrowed down with a 'matching' statement, but even without one, it will show OSPF packets (protocol 89) if present, revealing hello, DD, LSR, LSU, and LSAck packets. This makes it the correct tool for an administrator who suspects routing protocol updates are being misconfigured or lost, because it gives direct evidence of what is actually sent and received.

Why this answer

The 'monitor traffic interface' command in Junos captures live packets on a specified interface, allowing the administrator to inspect routing protocol packets (e.g., OSPF, BGP) in real time. This is the only option that directly captures and displays packet-level data to verify the next-hop IP address in routing protocol updates.

Exam trap

The trap here is that candidates often confuse log-based troubleshooting (Option A) with live packet capture, or they mistakenly think that viewing the forwarding table (Option B) or neighbor details (Option C) reveals the actual packet contents being transmitted, when in fact only a packet capture tool like 'monitor traffic' can show the raw protocol updates.

How to eliminate wrong answers

Option A is wrong because 'show log messages | match ospf' displays system log messages filtered for OSPF events, not actual packet captures; it shows control-plane events like neighbor state changes, not the contents of routing protocol packets. Option B is wrong because 'show route forwarding-table' displays the forwarding table entries (next-hop, interface) used for packet forwarding, not the routing protocol packets themselves; it shows the result of routing decisions, not the updates being sent. Option C is wrong because 'show ospf neighbor detail' displays OSPF neighbor state, router ID, and interface details, but does not capture or analyze the actual OSPF packets (e.g., Hello, LSU) on the wire.

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50

MCQmedium

An engineer configures two static routes to 172.16.0.0/16 with next-hops 10.0.1.1 and 10.0.2.1, both with the same preference and same metric. How does Junos handle traffic to this prefix?

A.It uses active/passive selection.

B.It load balances via ECMP.

C.It uses only the first configured route.

D.It drops traffic due to ambiguity.

AnswerB

Equal-cost multipath (ECMP) is the default behavior when multiple static routes share the same destination prefix and have identical preferences and metrics. Junos installs both routes in the routing table and uses a hash of packet header fields (e.g., source/destination IP) to select one of the equal next hops for each flow. This provides load balancing across the two paths without requiring any additional configuration. The routes are not mutually exclusive; they coexist and contribute to forwarding simultaneously.

Why this answer

Junos uses Equal-Cost Multipath (ECMP) when multiple static routes to the same destination prefix have identical preference (administrative distance) and metric. Since both routes to 172.16.0.0/16 have the same preference (default 5 for static routes) and metric (0 by default), Junos installs both in the forwarding table and load-balances traffic across the two next-hops (10.0.1.1 and 10.0.2.1) per-flow or per-packet depending on the configured hash algorithm.

Exam trap

The trap here is that candidates from a Cisco background often assume that only one static route can be active (like Cisco's behavior where the first route is used unless the next-hop fails), but Junos inherently supports ECMP for multiple static routes with equal metrics and preferences.

How to eliminate wrong answers

Option A is wrong because active/passive selection is a concept used in high-availability protocols like VRRP or in firewall failover, not in static route handling with equal preferences and metrics. Option C is wrong because Junos does not use only the first configured route; it evaluates all routes with the same preference and metric and installs them all for ECMP. Option D is wrong because there is no ambiguity; Junos explicitly supports multiple equal-cost routes to the same prefix and forwards traffic using ECMP rather than dropping it.

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51

MCQmedium

An engineer configures a static route to 192.168.0.0/16 with next-hop 172.16.1.1. The static route appears as 'hidden' in the routing table. What is the most likely cause?

A.The static route preference is set too high

B.The next-hop address 172.16.1.1 is unreachable

C.The static route has not been committed

D.The static route is a discard route

AnswerB

For a static route to be installed, its next-hop address must be resolvable through an entry in the routing table. If 172.16.1.1 is not reachable—for instance, the directly connected subnet is down or no route to that address exists—Junos marks the route as hidden because the next-hop cannot be resolved. The route remains in the configuration and can be seen with 'show route protocol static hidden', but it is not placed in the forwarding table. This is the exact reason the route appears as hidden.

Why this answer

In JUNOS, a static route with a next-hop that is not reachable (i.e., there is no active route to the next-hop) is automatically placed in a 'hidden' state. The most likely cause is that the next-hop 172.16.1.1 is unreachable.

Exam trap

The trap is that candidates might think a hidden route is due to protocol preference or commit issues. In JUNOS, 'hidden' specifically indicates a next-hop resolution failure, meaning the next-hop address is not reachable via any active route.

How to eliminate wrong answers

Option A is wrong because a high preference (administrative distance) would cause the route to be present in the routing table but not selected as active (it would be a 'non-preferred' route, not 'hidden'). Option C is wrong because an uncommitted configuration would not appear in the routing table at all; 'hidden' routes are committed but not usable due to a reachability issue. Option D is wrong because a discard route (e.g., 'static route next-hop discard') is explicitly configured and appears as an active 'discard' route in the routing table, not as 'hidden'.

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52

MCQmedium

Refer to the exhibit. Why is the route via 10.0.0.1 selected as the active route?

A.It has a lower metric

B.It has a lower cost

C.It is an older route

D.It has a lower preference

AnswerD

This is correct: route preference is the first and most decisive factor in Junos active-route selection. Preference is a numeric value assigned to each protocol (for example, static is 5 or 10, OSPF internal is 10, OSPF external is 150). When multiple routes to the same destination exist, Junos installs the one with the lowest preference, so the route via 10.0.0.1 with preference 10 wins over the less-preferred alternative with preference 150.

Why this answer

In Junos, the active route is selected based on the route preference value, where a lower preference is preferred. Since the route via 10.0.0.1 has a lower preference than the other route, it is chosen as active. This is a fundamental Junos routing decision process, distinct from metrics which are used within a single routing protocol.

Exam trap

The JNCIA-JUNOS exam often tests the misconception that metric (or cost) is the primary tiebreaker for route selection across all scenarios, but in Junos, preference is the first criterion for choosing between routes from different protocols or sources.

How to eliminate wrong answers

Option A is wrong because metric is used within a single routing protocol (e.g., OSPF cost, RIP hop count) to compare routes from the same protocol, not across different protocols or routes; Junos uses preference for inter-protocol route selection. Option B is wrong because cost is a specific metric for OSPF and does not determine active route selection across different routing protocols or sources. Option C is wrong because route age is not a factor in Junos active route selection; Junos does not prefer older or newer routes based on age.

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53

MCQeasy

Refer to the exhibit. How many next hops are installed for the 10.1.1.0/24 route?

A.4

B.2

C.3

D.1

AnswerB

Two next hops are installed for the 10.1.1.0/24 route because Junos OS leverages Equal-Cost Multipath (ECMP). When the routing table contains multiple paths to a destination with identical metrics, Junos selects all of them. These paths are then installed as distinct next hops in the forwarding table, enabling traffic to be load-balanced. This directly addresses the question regarding the number of *installed* next hops.

Why this answer

The route 10.1.1.0/24 has two next hops installed because the routing table shows two distinct next-hop addresses (e.g., 192.168.1.1 and 192.168.2.1) under the same route entry. In JUNOS, when equal-cost paths exist, the route is installed with multiple next hops, and the count reflects the number of unique next-hop entries, not the number of interfaces or paths in a load-balancing set.

Exam trap

The trap here is that candidates often count the number of interfaces or paths shown in the output (e.g., two interfaces with two IPs each) and mistakenly think each interface represents a separate next hop, when JUNOS counts only the unique next-hop IP addresses.

How to eliminate wrong answers

Option A is wrong because 4 would imply four next hops, but the exhibit shows only two next-hop addresses for this route, not four. Option C is wrong because 3 would require three next hops, but the routing table output clearly lists two next hops. Option D is wrong because 1 would indicate a single next hop, but the route has two next hops due to ECMP (Equal-Cost Multi-Path) being active.

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54

MCQeasy

A Juniper device receives several routes to the same destination prefix from different routing protocols. Which parameter is used first to select the active route?

A.Route preference (administrative distance)

B.Metric

C.AS path length

D.Local preference

AnswerA

Route preference (administrative distance) is the first criterion Junos uses when selecting the best route to a destination among routes from different routing protocols. Each protocol has a default preference value (e.g., OSPF 10, BGP 170), and the route with the lowest preference wins. Because these values are locally defined and universally comparable across protocols, they serve as the primary tie-breaker.

Why this answer

When a Juniper device receives multiple routes to the same destination prefix from different routing protocols, the route preference (also known as administrative distance) is the first tiebreaker used to select the active route. Each protocol has a default preference value (e.g., OSPF internal routes have a preference of 10, while static routes have a preference of 5), and the route with the lowest preference is chosen as active. This occurs before any metric or other path attribute is considered.

Exam trap

The trap here is that candidates often confuse route preference with metric, thinking that a lower metric from one protocol will automatically beat a higher metric from another protocol, but in reality, metric comparisons are only valid within the same routing protocol.

How to eliminate wrong answers

Option B is wrong because metric is only compared among routes from the same routing protocol (e.g., OSPF cost or BGP MED) and is not used to compare routes from different protocols. Option C is wrong because AS path length is a BGP-specific attribute used for path selection within BGP, not for comparing routes from different routing protocols. Option D is wrong because local preference is a BGP attribute used to influence outbound traffic within an AS and is only considered during BGP path selection, not across different routing protocols.

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55

MCQhard

An enterprise uses OSPF across multiple areas. To reduce routing table size in the backbone area, the engineer wants to advertise a single summary route for all subnets in area 2. Which configuration is appropriate?

A.Configure a virtual-link between area 2 and area 0

B.Configure a default route from area 2 using 'default-metric'

C.Use a static route for the summary and redistribute it into OSPF

D.Configure 'area 2 area-range 10.0.0.0/16' on the ABR

AnswerD

On an ABR, the 'area range' command summarizes routes from a specified area into a single aggregate prefix that is advertised to other areas. In this case, 'area 2 area-range 10.0.0.0/16' instructs the ABR to collapse all more-specific routes within 10.0.0.0/16 that belong to area 2 into one summary LSA. This reduces the number of routes in the global routing table of routers in other areas, while still allowing intra-area routes inside area 2 to remain detailed for local routing. This is the native and preferred OSPF mechanism for route summarization.

Why this answer

The 'area-range' command on an Area Border Router (ABR) allows you to summarize a set of routes from a specific area into the backbone (area 0) by advertising a single aggregate route (e.g., 10.0.0.0/16) instead of all individual subnets. This reduces the routing table size in area 0 while still providing reachability to all subnets in area 2.

Exam trap

The trap here is that candidates often confuse 'area-range' (which summarizes routes between areas) with 'virtual-link' (which fixes connectivity issues) or assume redistribution is needed for summarization, when OSPF's built-in ABR summarization is the correct and simplest method.

How to eliminate wrong answers

Option A is wrong because a virtual-link is used to connect a non-backbone area to area 0 when the area is physically disconnected, not for route summarization; it does not create a summary route. Option B is wrong because 'default-metric' is used to set the metric for default routes redistributed into OSPF, but it does not summarize area-specific subnets into a single route. Option C is wrong because using a static route and redistributing it into OSPF would create a separate external route (type 5 LSA) rather than a type 3 summary LSA, and it would not automatically summarize all subnets in area 2; it also adds administrative overhead and may cause suboptimal routing.

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56

MCQhard

Refer to the exhibit. Why is the static route not active?

A.The OSPF route has a lower metric.

B.The static route's next-hop is not reachable.

C.The static route is not committed.

D.The static route has a higher preference than the OSPF route.

AnswerD

Junos uses preference to select the best route to a destination when multiple protocols offer a route. The default preference for static is 15, while OSPF internal routes have a default preference of 10. A higher preference value means less preferred, so OSPF's route is chosen as active, and the static route becomes inactive (but still in the routing table). This explains why the static route appears but is not used for forwarding.

Why this answer

Junos uses route preference (administrative distance) to select the active route when multiple routes to the same destination exist. By default, OSPF has a preference of 10, while a static route has a preference of 5. Since a lower preference value is more preferred, the static route should normally be active.

However, the question indicates the static route is not active, which implies the static route's preference has been manually set higher than OSPF's preference (e.g., static route preference > 10), causing OSPF to be selected as the active route.

Exam trap

The trap here is that candidates often confuse metric with preference, assuming a lower OSPF metric would override a static route, but in Junos, preference is the primary tiebreaker between different routing protocols, not metric.

How to eliminate wrong answers

Option A is wrong because OSPF metric (cost) is only compared among OSPF routes; route preference is evaluated first before metric when comparing routes from different protocols. Option B is wrong because if the static route's next-hop were not reachable, the route would be hidden or marked as unreachable, not simply inactive; the exhibit would show a 'hidden' flag or the route would not appear in the routing table. Option C is wrong because if the static route were not committed, it would not appear in the configuration or routing table at all; the exhibit shows the route exists, so it has been committed.

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57

Multi-Selecthard

Which TWO configuration statements are valid for defining a static route on a Junos device?

Select 2 answers

A.set routing-options static route 10.0.0.0/8 discard

B.set routing-options static route 10.0.0.0/8 reject-all

C.set routing-options static route 10.0.0.0/8 qualified-next-hop 192.168.1.1 preference 10

D.set routing-options static route 10.0.0.0/8 next-hop 192.168.1.1 metric 10

E.set routing-options static route 10.0.0.0/8 passive

AnswersA, C

The `discard` action is a valid static route next-hop type in Junos, causing the router to silently drop packets that match the route without generating an ICMP unreachable message. This statement installs a route to 10.0.0.0/8 with a next-hop type of 'discard', effectively blackholing traffic—a common technique for preventing routing loops or intentionally dropping traffic. The syntax `set routing-options static route 10.0.0.0/8 discard` is fully valid and correctly configured.

Why this answer

Option A is correct because Junos supports the discard next-hop on a static route, which silently drops matching traffic and is configured exactly as set routing-options static route 10.0.0.0/8 discard. Option C is correct because qualified-next-hop is a valid Junos static-route next-hop type that allows a per-next-hop preference, so set routing-options static route 10.0.0.0/8 qualified-next-hop 192.168.1.1 preference 10 is syntactically valid. Option B is wrong because reject-all is not a valid Junos static-route next-hop keyword; the valid reject form is simply reject.

Option D is wrong because Junos static routes do not use a metric statement; route preference is set with preference, not metric. Option E is wrong because passive is not a valid static-route option in Junos.

Exam trap

The trap here is that candidates familiar with Cisco IOS may mistakenly use `metric` or `passive` keywords, which are not valid in Junos for static routes, or confuse `reject-all` with the correct `reject` action.

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58

MCQmedium

You configure an aggregate route for 172.16.0.0/16. What must exist for this aggregate to be active in the routing table?

A.A directly connected interface on that subnet

B.A static route to the aggregate prefix

C.A contributing route (more specific route within the aggregate range)

D.Nothing; the aggregate is always active once committed.

AnswerC

The one mandatory configuration for an aggregate route is a contributing route: any active route with a prefix that is more specific than 172.16.0.0/16 and whose destination lies within that aggregate's address space. Junos evaluates the routing table for such routes and installs the aggregate with a next hop derived from the selected contributor; without at least one contributor, the aggregate is not installed and cannot be advertised or used for packet forwarding. This requirement ensures the aggregate always has a valid forwarding path rather than becoming a black hole.

Why this answer

The correct option is C: a contributing route (a more specific route within the aggregate range) must exist for the aggregate to become active. In Junos, an aggregate route is only installed into the routing table when at least one more-specific route covered by the aggregate prefix is present in the routing table; for 172.16.0.0/16, that means a route such as 172.16.1.0/24 must be learned or configured. Option A is incorrect because a directly connected interface on the exact aggregate subnet is not required, and a more-specific connected route would itself serve as the contributing route.

Option B is incorrect because a static route to the aggregate prefix does not activate the aggregate and would conflict with the aggregate's purpose. Option D is incorrect because aggregate routes are not unconditionally active; they depend on the presence of contributing routes.

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59

Multi-Selecteasy

Which two statements are true about static routes on Juniper devices? (Choose two.)

Select 2 answers

A.A static route with a next-hop of an IP address requires that the next-hop be reachable.

B.Static routes can be configured with a qualified-next-hop to provide conditional routing.

C.A static route with a next-hop of an interface will be active even if the interface is down.

D.A static route with a preference of 10 is preferred over a static route with a preference of 5.

E.Static routes cannot be used for load balancing.

AnswersA, B

In Junos, a static route with a next-hop IP address is activated only when that next-hop is resolvable through an existing active route in the routing table. If the next-hop becomes unreachable (e.g., its connected interface goes down or the route to it disappears), the static route is marked inactive and no longer installs in the forwarding table. This ensures the router does not black-hole traffic by sending it to a dead next-hop.

Why this answer

Option A is correct because a static route whose next-hop is specified as an IP address is only installed in the routing table (and thus active) if that next-hop is resolvable and reachable via a route in inet.0; if the next-hop is unreachable, the route stays hidden. Option B is correct because Junos supports the qualified-next-hop statement, which lets you attach a separate preference to each next-hop of a static route, enabling conditional/backup routing where the secondary next-hop is used only when the primary becomes unreachable. Option C is wrong because a static route pointing at an interface (e.g., next-hop ge-0/0/0.0) is only active while that interface is up, so it is not active when the interface is down.

Option D is wrong because in Junos a lower preference value is preferred, so a route with preference 5 wins over one with preference 10. Option E is wrong because static routes can perform load balancing by configuring multiple next-hops (or multiple paths) for the same destination, which are then installed as equal-cost multipath entries.

Exam trap

The trap here is that candidates often assume a static route with a next-hop of an interface remains active regardless of interface state, but Junos strictly requires the interface to be up for the route to be installed.

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60

MCQeasy

A network administrator configures a default route using 'set routing-options static route 0.0.0.0/0 next-hop 10.0.0.1 preference 10' and later enables OSPF which also advertises a default route with default preference 150. Which route becomes active in the routing table?

A.Neither route becomes active due to conflicting protocols

B.Both routes are active for ECMP load balancing

C.Static route to 0.0.0.0/0 with next-hop 10.0.0.1

D.OSPF route to 0.0.0.0/0

AnswerC

The static route to 0.0.0.0/0 with next-hop 10.0.0.1 is the winning route. With a route preference of 10, it is more trustworthy than the OSPF default route’s preference of 150. Junos installs it in the inet.0 routing table and destination table, so it becomes the active default route.

Why this answer

The static route has a preference of 10, which is lower than OSPF's default preference of 150. Junos uses the route with the lowest preference value as the active route in the routing table. Therefore, the static default route becomes active.

Exam trap

The trap here is that candidates may think OSPF always overrides static routes or that both routes can be used for ECMP, but Junos uses preference values to select a single active route, and ECMP only applies when preferences are equal.

How to eliminate wrong answers

Option A is wrong because conflicting protocols do not prevent a route from becoming active; Junos selects the route with the lowest preference. Option B is wrong because ECMP load balancing requires equal preference values, and here the static route (preference 10) and OSPF route (preference 150) have different preferences, so only the best route is installed. Option D is wrong because the OSPF default route has a higher preference (150) than the static route (10), so it is not selected as active.

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