JN0-106 Routing Fundamentals Practice Test 2 — 15 Questions

Question 1

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

Accepted Answer

Route preference. Route preference (B) is correct because when multiple routing protocols offer routes to the same destination, the device compares administrative distance (route preference) values and installs the route from the protocol with the lowest value, such as directly connected (0), static (1), or OSPF (110) over RIP (120). Next-hop reachability (D) is correct because a route can only be active if its next-hop address is resolvable and reachable through an active interface; if the next hop is unreachable, the route is removed from the routing table even if it has the best preference. Metric (A) is not the deciding factor across different protocols—it is only used to compare routes within the same protocol. Route origin (C) is not a standard route-selection criterion, and local preference (E) is a BGP-specific attribute used only within BGP path selection, not across different protocols.

Answer

Metric

Answer

Route origin

Answer

Local preference

Question 2

A route is present in the routing table but is not active. Which three conditions could explain this? (Choose three.)

Accepted Answer

A route with a lower preference exists for the same destination.. Option A is correct because when two routes match the same destination prefix, the route with the higher preference value (lower priority) is not installed as the active route in the routing table, so it remains present but inactive. Option D is correct because a route whose next-hop cannot be resolved (for example, the next-hop IP is not reachable via any interface or ARP resolution fails) is kept in the table but marked inactive until the next-hop becomes reachable. Option E is correct because a static route configured with a qualified-next-hop is only active when that qualified next-hop is reachable; if the condition is not satisfied, the route stays in the table but is not used. Option B is not correct because a firewall filter typically discards or rejects traffic rather than hiding a route from the routing table, and Option C is not correct because an aggregate route can still be active and installed when it has a valid contributing or discard next-hop.

Answer

The route is hidden due to a firewall filter.

Answer

The route is an aggregate route.

Question 3

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

Accepted Answer

The next-hop address is not reachable in the routing table.. 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.

Answer

The static route has a high preference.

Answer

The outbound interface is not up.

Answer

The static route is not committed.

Question 4

Which JunOS command displays the active route for a specific destination along with the outgoing interface?

Accepted Answer

show route 10.0.0.1 exact. The 'show route <prefix> exact' command displays the active route entry for the exact destination prefix, including the outgoing interface and next-hop information. The 'exact' keyword ensures that only the route matching the specified prefix length is shown, which is essential for identifying the active forwarding path.

Answer

show route 10.0.0.1 active-path

Answer

show route 10.0.0.1 protocol static

Answer

show route 10.0.0.1 table inet.0

Question 5

A network has two equal-cost OSPF paths to 192.168.1.0/24. The engineer wants to enable per-flow load balancing. Which configuration element is required?

Accepted Answer

Add 'multipath' under 'routing-options' for OSPF. To enable per-flow load balancing across equal-cost OSPF paths in Junos, you must include the 'multipath' statement under [edit protocols ospf]. This allows OSPF to install multiple equal-cost routes. The default hash key (source/destination IP and optional Layer 4 ports) is then used for per-flow forwarding. The 'routing-options multipath' statement is used globally (e.g., for BGP or per-packet forwarding) and does not enable OSPF ECMP by itself.

Answer

Configure per-packet load balancing under the interface

Answer

Define a load-balancing hash-key including Layer 4 information

Answer

Set a higher preference on one path to force ECMP

Question 6

What is the default preference value of a directly connected (direct) route in JunOS?

Accepted Answer

0. In JunOS, directly connected routes have a default preference value of 0, which is the highest possible preference (lowest numerical value). This ensures that directly connected routes are always preferred over routes learned from any dynamic routing protocol, as they represent interfaces that are directly reachable on the local device.

Answer

10

Answer

170

Answer

100

Question 7

Which THREE conditions must be met for a route to be considered active in the JunOS routing table? (Choose three.)

Accepted Answer

The route is preferred based on protocol preference. Option C is correct because Junos selects the active route for a prefix by comparing protocol preferences (administrative distance), and the route with the lowest preference value wins; a route that loses this comparison is not active. Option E is correct because a route whose next hop is unresolvable or unreachable cannot be used and is therefore not active in the routing table. Option D is correct because an active route is the one that Junos installs into the forwarding table (the Packet Forwarding Engine) for actual packet forwarding. Option A is not required, since multiple routes for the same prefix can exist and one is still selected as active. Option B is not a Junos condition, as Junos does not use a generic 'trusted protocol' concept to determine route activity; it relies on preference, next-hop reachability, and forwarding-table installation.

Answer

The route is the only route for the prefix

Answer

The route is from a trusted protocol

Question 8

Refer to the exhibit. How many active routes exist for 10.1.1.0/24?

Accepted Answer

1. The route 10.1.1.0/24 appears in the routing table with a next-hop of 192.168.1.1 and a preference of 5 (directly connected). Only one active route is present because the routing table shows a single entry for this prefix. Junos selects the active route based on the lowest preference value; here, there is no competing route, so only one route is active.

Answer

2

Answer

0

Answer

3

Question 9

A router has multiple equal-cost paths to the same destination. Which statement describes how Junos load balances traffic across these paths?

Accepted Answer

Junos uses per-flow load balancing based on source and destination IP and port.. When multiple equal-cost paths exist, Junos uses per-flow load balancing by default. The default hash algorithm uses the source and destination IP addresses (Layer 3) to select a next hop. Source and destination ports are not included unless you explicitly configure load-balancing hash keys to include Layer 4 information. This ensures packets of the same flow are consistently forwarded to the same next-hop.

Answer

Junos uses the route with the lowest next-hop IP.

Answer

Junos installs only one route and ignores the others.

Answer

Junos uses per-packet load balancing by default.

Question 10

A router is running OSPF and iBGP. Both protocols learn a route to 10.0.0.0/8. The OSPF route is in the routing table with a preference of 10, and the iBGP route has a preference of 170. Which event would cause the iBGP route to become active?

Accepted Answer

The OSPF route is withdrawn.. Both A and D correctly cause the iBGP route to become active. The question must be updated to either 'Which two events' or to remove one of the correct options. The current answer key with both is not appropriate for a single-answer exam question.

Answer

Both A and C.

Answer

The iBGP route's metric is lower.

Question 11

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?

Accepted Answer

Configure a static route to 10.1.1.0/24 with next-hop 192.168.1.1 and preference 5.. 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.

Answer

Configure the dynamic protocol to export the route with a metric of 1.

Answer

Configure a filter to reject the dynamic route.

Answer

Configure a static route to 10.1.1.0/24 with next-hop 192.168.1.1 and preference 15.

Question 12

Which THREE factors are considered when Junos selects the active route among multiple routes to the same destination?

Accepted Answer

Metric. Junos route selection first compares the protocol preference (administrative distance) of each candidate route, so option E (Preference) is correct because the route with the lowest preference value is preferred before any other tiebreaker. If preferences are equal, Junos compares the metric (cost) associated with each route, making option A (Metric) correct since the lower metric wins within the same protocol. When preference and metric are identical, Junos uses the next-hop address as a deterministic tiebreaker, so option D (Next-hop address) is correct because the route with the lower next-hop IP address is selected. Option B (Route age) is not used in Junos route selection, as Junos does not prefer older or newer routes by default. Option C (Interface bandwidth) is not a direct selection factor; bandwidth may influence a protocol's metric, but it is not independently evaluated during active route selection.

Answer

Route age

Answer

Interface bandwidth

Question 13

Which two static route options result in traffic being dropped at the router? (Choose two.)

Accepted Answer

reject. In Junos, a static route with the reject option (B) causes matching packets to be dropped while the router returns an ICMP unreachable message to the source, which is why it results in traffic being dropped at the router. The discard option (D) also drops matching traffic, but silently, without sending any ICMP notification back to the sender. Both reject and discard are therefore the two static route options that terminate traffic at the router rather than forwarding it. The install option (A) simply installs a route into the routing table and does not drop traffic, next-table (C) forwards traffic to a different routing table for further lookup, and resolve (E) resolves the next hop via another route rather than dropping packets.

Answer

install

Answer

next-table

Answer

resolve

Question 14

A network engineer is managing a hub-and-spoke OSPF network for a retail company. The hub router (hub01) is at the data center with a loopback address 10.99.99.99. The spoke router (spoke01) is at a branch office and connects to hub01 via two links: a primary T1 link on interface ge-0/0/0.0 and a backup LTE link on interface lte-0/0/0.0. Both links are in area 0. Recently, the spoke router began sending traffic to the hub's loopback over the LTE link instead of the T1 link, causing higher latency and data charges. The engineer checks the routing table on spoke01 and sees that the route to 10.99.99.99/32 has two equal-cost next-hops: one via ge-0/0/0.0 and one via lte-0/0/0.0. The engineer wants to ensure that only the T1 link is used under normal conditions, with the LTE link as a backup. Which action should the engineer take to achieve this?

Accepted Answer

Increase the OSPF cost on interface lte-0/0/0.0 to a value higher than the cost on ge-0/0/0.0.. The correct action is D: increase the OSPF cost on interface lte-0/0/0.0 to a value higher than the cost on ge-0/0/0.0. OSPF selects the lowest-cost path, so raising the LTE interface's cost makes the T1 path preferred while still allowing the LTE link to be used as a backup if the T1 fails. Option A would also make the T1 preferred, but it does not explicitly ensure the LTE cost is higher and is less precise for this scenario. Option B is wrong because a static route with a lower preference than OSPF would not be installed while OSPF routes exist, and it would not provide dynamic backup. Option C is irrelevant because OSPF priority only affects designated router election on broadcast networks, not path selection.

Answer

Decrease the OSPF cost on interface ge-0/0/0.0 to 1.

Answer

Configure a static route to 10.99.99.99/32 with next-hop referencing the T1 interface and a lower preference than OSPF.

Answer

Set the OSPF priority on ge-0/0/0.0 to 128 to influence the designated router election.

Question 15

A service provider operates a Juniper MX router that receives a default route from two different ISPs via EBGP. Both ISPs advertise 0.0.0.0/0 with the same local preference (100), same AS path length, and same metric. The network administrator wants to load balance outgoing traffic across both ISPs for redundancy and bandwidth utilization. After applying the configuration, the administrator checks the routing table and sees that only one default route is active, the one from ISP-A. The other route from ISP-B is present but not active. The administrator verifies that both routes have the same preference (170) and same BGP attributes. The ISP links are different: ISP-A is connected via interface ge-0/0/0.0 with next-hop 10.1.1.2, and ISP-B via interface ge-0/0/1.0 with next-hop 10.2.2.2. What is the most likely reason that both routes are not active and load-balanced?

Accepted Answer

The BGP routes are from different autonomous systems.. By default, Junos BGP does not load balance routes from different autonomous systems. To enable multipath across different ASes, the 'multipath multiple-as' command must be configured under BGP. Option A is irrelevant. Option B is not a cause because different next-hops can be load-balanced under multipath. Option D is the solution, not the cause. Therefore, the most likely cause is that the routes are from different ASes.

Answer

The router has 'no-policy-statistics' enabled on the BGP sessions.

Answer

The BGP routes have different next-hop addresses.

Answer

The router is configured with 'multipath multiple-as' under BGP.