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CCNA Routing Fundamentals Questions

36 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
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

Preference is the primary selection criterion.

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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3
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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4
Multi-Selectmedium

Which two factors determine whether a route is active for a given destination when multiple routes from different protocols exist? (Choose two.)

Select 2 answers
A.Metric
B.Route preference
C.Route origin
D.Next-hop reachability
E.Local preference
AnswersB, D

Route preference is used to compare routes from different protocols; lower preference is preferred.

Why this answer

B is correct because Junos uses route preference (administrative distance) as the primary tiebreaker when multiple routing protocols offer routes to the same destination. The route with the lowest preference value is installed into the routing table as the active route. D is correct because even if a route has the best preference, it must have a reachable next hop to be considered active; if the next hop is unreachable, the route is hidden and not used.

Exam trap

The trap here is that candidates often confuse metric with preference, thinking metric is used to compare routes from different protocols, but Junos uses preference as the first tiebreaker, and metric only applies within the same protocol.

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5
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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6
Drag & Dropmedium

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

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

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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7
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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8
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 is only installed if the next-hop is reachable via an active route.

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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9
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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10
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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11
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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12
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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13
MCQhard

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

A.The static route has a high preference.
B.The outbound interface is not up.
C.The static route is not committed.
D.The next-hop address is not reachable in the routing table.
AnswerD

For a static route with a next-hop IP address, Junos performs recursive route resolution: it looks up that next-hop address in the routing table to find a valid, active route to that address. The command 'show route 10.10.10.1' returns no output, proving there is no route in the table to the next-hop. Without a route to the next-hop, the static route cannot be installed as active, even though it is present in the routing table as an eligible route. This is exactly why the route is inactive.

Why this answer

For a static route to be active in the JUNOS routing table, the next-hop address must be reachable via an active route in the routing table. If the next-hop is not reachable, the static route is considered invalid and will not be installed as active, even if the outbound interface is up and the configuration is committed.

Exam trap

The trap here is that candidates often assume a static route is always active once configured and committed, forgetting that JUNOS requires the next-hop to be reachable in the routing table for the route to be installed.

How to eliminate wrong answers

Option A is wrong because a high preference (i.e., a less preferred route) does not prevent a static route from being active; it only affects route selection among multiple routes to the same destination. Option B is wrong because the outbound interface being down would cause the route to be inactive, but the question specifically states the static route is not active due to the next-hop not being reachable, not the interface state. Option C is wrong because the static route must be committed to be considered for activation; if it were not committed, it would not appear in the configuration at all, but the exhibit shows the route is configured.

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14
Drag & Dropmedium

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

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

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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15
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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16
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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17
Multi-Selectmedium

Which two statements about static routes in Junos OS are correct?

Select 3 answers
A.A static route with a next-hop of 127.0.0.1 is an unreachable route.
B.Static routes have a default preference of 5.
C.A static route configured with a next-hop of an interface name (e.g., ge-0/0/0) uses Address Resolution Protocol (ARP) to resolve the next-hop MAC address.
D.A static route with a next-hop of 0.0.0.0 is a discard route.
E.Static routes can have a preference value of 0.
AnswersB, C, D

Correct. Static routes in Junos OS have a default preference of 5.

Why this answer

Static routes have a default preference of 5 in Junos OS. Option C is correct: when a static route uses an interface as the next-hop (e.g., ge-0/0/0), the router uses ARP to resolve the MAC address of the next-hop device. Option D is correct: a static route with a next-hop of 0.0.0.0 is a discard route that silently drops packets.

Option A is incorrect: a static route with a next-hop of 127.0.0.1 creates a reject route (sends ICMP unreachable), not an unreachable route. Option E is incorrect: static routes cannot have a preference value of 0 because preference 0 is reserved for directly connected routes.

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18
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

Direct routes have preference 0, which is the lowest possible, so they are always preferred.

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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19
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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20
MCQhard

A network must forward traffic to 10.1.1.0/24 through a specific next-hop 192.168.1.1, even if a dynamic route with a lower preference is available. Which configuration will achieve this?

A.Configure the dynamic protocol to export the route with a metric of 1.
B.Configure a static route to 10.1.1.0/24 with next-hop 192.168.1.1 and preference 5.
C.Configure a filter to reject the dynamic route.
D.Configure a static route to 10.1.1.0/24 with next-hop 192.168.1.1 and preference 15.
AnswerB

Preference 5 is lower than most dynamic defaults, so static will be active.

Why this answer

A static route can be configured with a preference value lower than any dynamic routing protocol's default preference. In Junos, the default preference for OSPF internal routes is 10, for IS-IS level 1 is 15, for RIP is 100, and for BGP is 170. By setting the static route to 10.1.1.0/24 with next-hop 192.168.1.1 and preference 5, it will have a lower preference value than these defaults.

Therefore, even if a dynamic route with a lower preference (i.e., a smaller number but still greater than 5) exists, the static route will be installed in the routing table and used for forwarding, satisfying the requirement to always forward traffic through the specified next-hop.

Exam trap

The trap here is that candidates often confuse metric with preference (administrative distance) and assume that a lower metric on a dynamic route will make it preferred over a static route, or they mistakenly think a higher preference value on a static route (like 15) still makes it preferred over OSPF (10).

How to eliminate wrong answers

Option A is wrong because exporting a dynamic route with a metric of 1 does not change the route's preference; metric is used for route selection among routes from the same protocol, not for comparing routes from different protocols. Option C is wrong because rejecting the dynamic route with a filter would prevent it from being installed, but it does not ensure that the desired static route is used; additionally, it is an indirect and less reliable method compared to setting a lower preference on the static route. Option D is wrong because a preference of 15 is higher than the default preference of OSPF (10) and IS-IS (15), so the static route would not be preferred over an OSPF route (preference 10) and would tie with IS-IS (preference 15), failing to guarantee that traffic is forwarded through 192.168.1.1.

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21
MCQeasy

You are a network engineer for a company that uses two Juniper routers, R1 and R2, connected via an Ethernet link. R1 and R2 are running OSPF in the same area, and R2 also has an eBGP session with a service provider to reach the internet. On R1, you have configured a static route to the subnet 172.16.10.0/24 with a next-hop of 192.168.1.2, which is the IP address of R2's interface facing R1. You have verified that the static route is configured correctly in the configuration, but traffic from R1 to 172.16.10.0/24 is not being forwarded. You check the routing table on R1 and see that the static route is present but marked as 'hidden'. You also notice that R1 has an OSPF-learned route to 192.168.1.0/30 (the link between R1 and R2) with a cost of 1. What is the most appropriate next troubleshooting step?

A.Disable the eBGP session on R2 to remove the BGP routes from the routing table.
B.Increase the static route's preference to a lower value (e.g., 4).
C.Configure a more specific static route to 172.16.10.0/24 with a mask of /25.
D.Check if the next-hop IP 192.168.1.2 is reachable via the directly connected interface.
AnswerD

Correct: the next-hop unreachability is the most common cause of a hidden static route; verifying reachability (e.g., ping, ARP) will identify the issue.

Why this answer

A static route becomes hidden in Juniper's routing table when the next-hop is considered unreachable. Although R1 has an OSPF-learned route to the subnet 192.168.1.0/30, the router performs a recursive lookup to ensure the next-hop IP 192.168.1.2 is reachable via a directly connected interface or a valid route. In this case, the next-hop is directly connected, so the most likely cause is that the interface is down, or there is an ARP resolution issue, or a firewall filter blocking ARP.

Option D directs you to check if the next-hop is reachable via the directly connected interface, which is the appropriate first troubleshooting step. Option A is incorrect because disabling eBGP on R2 does not affect R1's static route next-hop reachability. Option B is incorrect because lowering preference would not resolve a hidden route; hidden routes are not considered for forwarding regardless of preference.

Option C is incorrect because making the route more specific does not address the reachability issue.

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22
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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23
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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24
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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25
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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26
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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27
MCQhard

Your company operates a dual-homed network with two Juniper MX routers (R1 and R2) each connected to a different ISP. R1 uses BGP to receive a default route from ISP-A (preference 170), and R2 uses BGP to receive a default route from ISP-B (preference 170). Additionally, both routers have a static default route pointing to a local next-hop (192.0.2.1) with preference 5 for backup. R1 and R2 are connected via an internal link (10.0.0.0/30) and run OSPF to exchange internal routes. You notice that traffic from internal hosts is always exiting via R1's ISP-A link, even when R1's BGP session to ISP-A goes down. The OSPF routes are preferred. You want traffic to fail over to R2's ISP-B link when R1 loses its BGP default. Which configuration change should you make?

A.Increase the preference of the BGP default routes to 180 so that the static default is always preferred.
B.Configure a routing policy on R2 to reject the default route from ISP-B, forcing all traffic through R1.
C.Remove the static default route and rely on OSPF to propagate a default route from the router with the active BGP session.
D.Configure the static default route with a preference of 180 so that the BGP default routes (pref 170) are preferred when available.
AnswerD

This ensures BGP default is used when up, and OSPF routes to R2's default become active when R1's BGP is down.

Why this answer

The static default route currently has a preference of 5, making it preferred over the BGP default (preference 170) even when the BGP route is available. By raising the static default's preference to 180 (higher than BGP's 170), the BGP default will be chosen when present, and the static default will only be used as a backup when BGP is unavailable. This ensures traffic fails over to R2's ISP-B link when R1 loses its BGP default, as OSPF will propagate the default from R2.

Exam trap

The trap here is that candidates often assume static routes with a lower preference are always better, but the question requires the static route to act as a backup, so it must have a higher preference than the BGP route to be less preferred when the BGP route is available.

How to eliminate wrong answers

Option A is wrong because increasing the BGP default preference to 180 would make it less preferred than the static default (preference 5), causing the static route to always be used, which does not solve the failover issue. Option B is wrong because rejecting the default route from ISP-B on R2 would prevent R2 from having any default route, breaking failover entirely and not addressing the preference problem on R1. Option C is wrong because removing the static default route would leave no backup path; OSPF does not automatically propagate a default route unless explicitly configured with a default-information originate statement, and even then, the OSPF default would have a preference of 10 (or 150 for external routes), which could still be preferred over BGP's 170, potentially causing the same issue.

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28
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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29
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

The reason given is 'next hop unreachable', so the next-hop is not reachable.

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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30
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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31
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

If the next-hop is not in the routing table, the static route is not active.

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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32
MCQhard

You are the network engineer for a mid-sized enterprise with a Juniper MX router running Junos. The router has two uplinks to the internet: one to ISP-A via ge-0/0/0 (10.0.0.1/30) and one to ISP-B via ge-0/0/1 (10.0.0.5/30). You have configured static default routes to both ISPs: one to 10.0.0.2 and one to 10.0.0.6. Both routes have the same preference (default 5) and metric. You enabled ECMP to load-balance outbound traffic. After testing, you notice that all traffic is being sent only to ISP-A, and none to ISP-B. You verify that both interfaces are up and that the next-hop addresses are reachable. You check the routing table and see both routes are active but with different next-hop counts. What is the most likely cause of the traffic not being load-balanced?

A.One of the static routes resolves to multiple next hops, causing imbalance.
B.ECMP is not enabled in the forwarding-options.
C.The route to ISP-B is not active.
D.Hash-based load balancing requires per-packet configuration.
AnswerA

If one route resolves to multiple next hops, it may appear as multiple routes, skewing load balancing.

Why this answer

When both static default routes have the same preference and metric, Junos installs both in the routing table. However, ECMP load-balancing requires that each route resolve to a single next hop. If one static route resolves to multiple next hops (e.g., through a recursive lookup to a prefix with multiple paths), the route with a single next hop (ISP-A) becomes the sole active path for forwarding, while the multi-next-hop route (ISP-B) is not used for load balancing.

This explains why all traffic goes to ISP-A despite both routes being present.

Exam trap

The trap here is that candidates assume both routes are equally valid for ECMP simply because they appear in the routing table, but they overlook how recursive resolution can cause one route to have multiple next hops, breaking the equal-cost multipath condition.

How to eliminate wrong answers

Option B is wrong because ECMP is enabled by default in Junos when multiple equal-cost routes exist; no explicit 'forwarding-options' configuration is required for basic ECMP. Option C is wrong because the scenario states both routes are active in the routing table, so the route to ISP-B is indeed active. Option D is wrong because hash-based load balancing is the default behavior for ECMP in Junos; per-packet configuration is not needed for load balancing to occur, and the issue here is not about load-balancing mode but about next-hop resolution.

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33
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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34
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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35
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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36
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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