JN0-106 Routing Fundamentals Practice Test 2 — 15 Questions

Question 1

Which TWO statements are true about static routes in Junos?

Accepted Answer

Static routes remain in the routing table even if the next hop is unreachable.. Static routes in Junos have a default preference of 5, not 10 (which is the default for OSPF internal routes). They remain in the routing table even if the next hop becomes unreachable because Junos uses a 'passive' route model; the route is only removed if explicitly deleted or if a better route is learned via a routing protocol. This behavior is controlled by the 'no-readvertise' and 'passive' attributes of static routes.

Answer

Static routes have a default preference value of 10.

Answer

Static routes require a routing protocol to be activated.

Answer

Static routes are automatically updated if the network topology changes.

Question 2

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?

Accepted Answer

show route 0.0.0.0/0. 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.

Answer

show route 192.168.1.2

Answer

ping 192.168.1.2

Answer

show route protocol static

Question 3

Match each Junos routing protocol to its primary characteristic.

Accepted Answer

OSPF: Uses link-state advertisements to build a topology database. OSPF and IS-IS are link-state protocols. BGP is path-vector. RIP is distance-vector. Static routes are manually configured. Common confusions include mixing link-state with distance-vector or mislabeling BGP.

Answer

IS-IS: Uses a distance-vector algorithm with split horizon

Answer

Static route: Learned dynamically through routing protocols

Answer

BGP: Uses distance-vector algorithm with link-state updates

Question 4

Match each Junos configuration hierarchy to its function.

Accepted Answer

system: Configures system-wide parameters such as hostname and time.. In Junos, 'system' manages hostname and time, 'interfaces' configures ports, 'protocols' handles routing protocols, and 'security' manages firewall policies. Common confusions include swapping these definitions.

Answer

system: Configures routing protocols like OSPF and BGP.

Answer

interfaces: Configures security policies and zones.

Question 5

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?

Accepted Answer

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

Answer

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

Answer

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

Answer

Modify the load-balance configuration under forwarding-options.

Question 6

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?

Accepted Answer

The next-hop 192.168.1.1 is not reachable.. 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.

Answer

The route preference is set to 170.

Answer

The route is not exported into the forwarding table.

Answer

The router already has a default route learned via DHCP.

Question 7

A static route with a next-hop of 10.0.0.1 is configured, but the route is not appearing in the active routing table. The output of `show route 10.0.0.1` shows that 10.0.0.1 is reachable via an OSPF route with preference 10. What is the most likely reason the static route is not active?

Accepted Answer

The static route has a higher preference than OSPF.. In Junos, OSPF internal routes have a default preference of 10, while static routes have a default preference of 5 (lower is more preferred). If a static route is not active despite its next-hop being reachable, it is likely because the static route has been configured with a higher preference value (e.g., >10), making it less preferred than the OSPF route. The `show route` output confirms the OSPF route is active with preference 10, so the static route must have a preference higher than 10 to be inactive.

Answer

The OSPF route has a lower metric than the static route.

Answer

The static route's next-hop is not directly connected.

Answer

The static route is configured with a qualified-next-hop that fails.

Question 8

A Juniper MX router is configured with multiple routing instances. In which scenario would an interface be automatically placed in a routing instance?

Accepted Answer

When the interface is associated with the default instance.. In Junos, all interfaces automatically belong to the default routing instance (inet.0) unless explicitly assigned to a different routing instance via the `interface` statement. Therefore, the scenario where an interface is automatically placed in a routing instance is when it is associated with the default instance, making option B correct.

Answer

When the interface is configured with an IP address from the instance's address family.

Answer

When the interface is configured under the instance's `interface` statement.

Answer

When the routing instance type is virtual-router and the interface is a physical interface.

Question 9

A network engineer is troubleshooting a BGP routing issue. The router receives a route to 172.16.0.0/16 from two BGP peers with different local preferences. The route from peer A has local preference 200, and from peer B has local preference 100. The router selects the route from peer A. What is the next step in BGP path selection if the local preferences were equal?

Accepted Answer

Compare the AS path length.. B is correct because in BGP path selection, after comparing local preference (highest wins), the next tiebreaker is the shortest AS path length. If local preferences are equal, the router compares the AS path length, selecting the route with fewer AS numbers. This is defined in RFC 4271 and is the second step in the BGP decision process.

Answer

Compare the MED.

Answer

Compare the IGP metric to the next-hop.

Answer

Compare the origin code.

Question 10

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

Accepted Answer

A static route with a next-hop of an IP address requires that the next-hop be reachable.. A static route with a next-hop IP address requires the next-hop to be reachable via a connected or active route in the routing table; otherwise, the route is not installed. This ensures that the router does not forward traffic to an unreachable destination, maintaining routing integrity.

Answer

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

Answer

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

Answer

Static routes cannot be used for load balancing.

Question 11

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.. A route with a lower preference (administrative distance) is preferred for the same destination prefix. In JUNOS, the route with the lowest preference value is installed as the active route in the forwarding table. If a route has a higher preference, it remains in the routing table as a backup but is not marked as active.

Answer

The route is hidden due to a firewall filter.

Answer

The route is an aggregate route.

Question 12

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?

Accepted Answer

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

Answer

Neither route becomes active due to conflicting protocols

Answer

Both routes are active for ECMP load balancing

Answer

OSPF route to 0.0.0.0/0

Question 13

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 14

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 15

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?

Accepted Answer

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

Answer

Configure a virtual-link between area 2 and area 0

Answer

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

Answer

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