JN0-106 Routing Fundamentals Practice Test 3 — 15 Questions

Question 1

A network engineer is troubleshooting a connectivity issue between two directly connected routers, R1 and R2. Both routers have IP addresses configured on their respective interfaces, and the interfaces are up. However, 'ping 192.168.1.2 source 192.168.1.1' from R1 fails. The engineer checks the routing table on R1 and sees a static route to 0.0.0.0/0 via a different next-hop, but no route for the 192.168.1.0/24 network. What is the most likely cause?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

The route to the directly connected network is missing from the routing table, possibly because the interface is not properly configured or the link is down.. In Junos, a directly connected route is installed in the routing table only when the interface is operationally up and has a valid IP configuration. If no route for 192.168.1.0/24 exists, the interface is not operationally up (e.g., no carrier) or the IP configuration is incorrect, even if the interface shows as administratively up. Therefore, the missing route is the symptom, and the underlying cause is an interface that is not fully operational or is misconfigured.

Answer

The ARP cache is stale and needs to be cleared.

Answer

The interface is not configured with an IP address.

Answer

A security policy is blocking ICMP traffic between the two routers.

Question 2

You are managing a small branch office with a Juniper SRX firewall that connects to the internet via a single ISP. The internal network uses 192.168.1.0/24. You need to configure a default route so that all internet-bound traffic goes to the ISP's next-hop 203.0.113.1. The SRX has two interfaces: ge-0/0/0 (untrust) with IP 203.0.113.2/30 and ge-0/0/1 (trust) with IP 192.168.1.1/24. You add the following configuration: 'set routing-options static route 0.0.0.0/0 next-hop 203.0.113.1'. After committing, devices on the trust network can ping the internet (e.g., 8.8.8.8) successfully. However, users report that they cannot access a specific public website hosted at 198.51.100.10. You verify that the SRX can reach that IP via ping and traceroute. What is the most likely cause of this issue?

Accepted Answer

The return traffic from the website is not reaching the SRX, possibly due to asymmetric routing or the website's firewall blocking the SRX's source IP.. The correct answer is B: the return traffic from the website is not reaching the SRX, possibly due to asymmetric routing or the website's firewall blocking the SRX's source IP. Since the SRX itself can ping and traceroute 198.51.100.10 successfully, the default route and next-hop 203.0.113.1 are working, and the SRX's own traffic is being source-NATed to 203.0.113.2; the failure is therefore on the return path or at the remote host, not in the local routing table. Option A is wrong because outbound traffic from the trust network is translated to the untrust interface IP via source NAT, and the SRX's own ping already proves reachability. Option C is wrong because the default route is present and functional, as demonstrated by successful pings to 8.8.8.8 and 198.51.100.10. Option D is wrong because no more specific static route is mentioned, and if one existed it would likely also break the SRX's own ping to that IP.

Answer

The SRX's source IP for outbound traffic is incorrect; it should use the untrust interface IP but is using the trust IP.

Answer

The default route is missing; the ISP must be configured as a static route.

Answer

There is a more specific static route to 198.51.100.0/24 with a different next-hop causing traffic to be sent elsewhere.

Question 3

A service provider is migrating from a legacy core network to Juniper MX series routers. In the new design, each MX router runs OSPF as the IGP with a single backbone area 0 and multiple non-backbone areas for customer aggregation. The network uses route summarization at area border routers (ABRs) to reduce routing table size. During testing, engineers notice that some customer prefixes from area 1 are not being propagated to the backbone area, even though the ABR has a valid route to those prefixes and has been configured with 'area 1 range 192.168.0.0/16'. The ABR is an MX240 running Junos 21.4R1. The 'show ospf route' command on the ABR shows the individual customer prefixes (e.g., 192.168.1.0/24) in the OSPF routing table, but the summary route is not present in the backbone area's database. Additionally, 'show ospf database summary' on a backbone router does not show the summary LSA for 192.168.0.0/16. What is the most likely cause?

Accepted Answer

The individual prefixes from area 1 may not be installed in the inet.0 routing table on the ABR, possibly due to a missing OSPF adjacency or a route filter blocking them.. The 'area range' command requires the individual prefixes to be present in the inet.0 routing table on the ABR; if they are missing due to a missing OSPF adjacency or a route filter, the summary LSA is not generated. Option A is incorrect because the summary LSA is type 3, not type 5, and an external route does not suppress the summary. Option B is incorrect because the 'area range' command does not require an interface in the area; it summarizes routes learned from the area. Option C is incorrect because the 'area range' command takes effect immediately without requiring a restart or clearing of the OSPF database.

Answer

The summary LSA is being suppressed because the ABR is also advertising a type 5 external route for the same prefix.

Answer

The ABR has no interface in area 1 that matches the summary range; the 'area range' command requires a directly connected interface.

Answer

The 'area range' command only works after a routing process restart; a 'clear ospf database' is required to regenerate LSAs.

Question 4

You are a network engineer at a company that uses a pair of Juniper EX4300 switches in a virtual chassis (VC) configuration for the campus core. The VC is running OSPF with a single area and has multiple uplinks to an upstream router. The router is advertising a default route via OSPF. You want all inter-vlan traffic within the VC to be switched, but internet-bound traffic should be routed via the default route. You notice that some VLANs are not able to reach the internet while others can. All VLANs have a default gateway on the VC, which is the same IP (the VC's management IP). Users in the failing VLANs can ping the default gateway but cannot ping the upstream router's interface IP. What is the most likely cause?

Accepted Answer

The IRB interface for the failing VLANs does not have OSPF enabled, so the upstream router does not have a route to those subnets, and return traffic is dropped.. The IRB interface for the failing VLANs does not have OSPF enabled, so the upstream router does not have a route to those subnets and return traffic is dropped. In a Juniper VC, each VLAN's Layer 3 gateway is an IRB interface, and OSPF must be enabled on each IRB (or the relevant interface) for its subnet to be advertised into OSPF; if it is not, the upstream router will not know how to route return traffic to that VLAN, even though users can ping their local default gateway. Options A, B, and D do not fit: the VC is not an ABR in a single-area OSPF setup, MAC learning is not the issue because the users can reach the gateway, and a static default route would not selectively affect only some VLANs' return traffic.

Answer

The VC is configured as an OSPF area border router and is not creating a summary for the failing VLANs.

Answer

The VC's MAC address table is not learning the upstream router's MAC address on the correct VLAN.

Answer

The default route from OSPF is not being installed because there is a static default route with lower preference.

Question 5

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

Accepted Answer

Static routes have a default preference of 5.. 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.

Answer

A static route with a next-hop of 127.0.0.1 is an unreachable route.

Answer

Static routes can have a preference value of 0.

Question 6

Refer to the exhibit. A network administrator configured a static route to 10.0.0.0/24 with next-hop 192.168.1.1. The route is not appearing in the active routing table. What is the most likely reason?

Accepted Answer

The next-hop address is not reachable.. Option A is correct because a static route with a specified next-hop is only installed in the active routing table if that next-hop address is resolvable and reachable via a connected/recursive route; if 192.168.1.1 is not reachable, the route stays inactive. Option B is wrong because a reject route is a deliberately configured static route type that discards traffic, not the default behavior of a normal static route. Option C is wrong because OSPF routes typically have a higher administrative distance (110) than static routes (1), so OSPF would not override a static route. Option D is wrong because static route preference (administrative distance) being too high would only matter if a competing route existed, and it does not explain why the route is absent from the table.

Answer

The route is a reject route.

Answer

The route is being overridden by an OSPF route with lower preference.

Answer

The static route preference is too high.

Question 7

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?

Accepted Answer

Check if the next-hop IP 192.168.1.2 is reachable via the directly connected interface.. A static route marked 'hidden' in Junos means the next-hop is unresolvable — the router cannot find a route to the next-hop IP in its routing table. The most appropriate next step is to verify whether 192.168.1.2 is reachable via a directly connected interface, since the OSPF-learned route to 192.168.1.0/30 should provide that reachability but may be missing or inactive.

Answer

Disable the eBGP session on R2 to remove the BGP routes from the routing table.

Answer

Increase the static route's preference to a lower value (e.g., 4).

Answer

Configure a more specific static route to 172.16.10.0/24 with a mask of /25.

Question 8

A network engineer is examining the routing table on a Junos device and sees an entry for 10.0.0.0/24 with two next-hops: 192.168.1.1 and 192.168.1.2, both with the same preference. The engineer wants traffic destined to 10.0.0.0/24 to be load-balanced across both next-hops. What must be configured on the Junos device?

Accepted Answer

Ensure that the routing protocol or static configuration allows multiple next-hops for the same prefix.. Load balancing in Junos happens automatically when multiple equal-cost next-hops exist for a destination. For static routes, you can define multiple next-hops with the same preference. For dynamic routing protocols, you must enable multipath (e.g., 'multipath' under OSPF or BGP) to allow multiple paths to be installed. The forwarding table then uses per-flow load balancing by default.

Answer

Enable load balancing by setting the 'load-balance per-packet' option under the routing-options stanza.

Answer

Configure a policy that sets the next-hop to both addresses.

Answer

Enable per-packet load balancing under the forwarding-options stanza.

Question 9

A Junos router is configured with OSPF and BGP. The network administrator wants to verify the routing table and ensure that OSPF routes are preferred over BGP routes for the same prefix. Which two statements are correct about route preference in Junos? (Choose two.)

Accepted Answer

You can modify the default preference of BGP to be lower than OSPF using a routing policy.. Junos uses preference values to select among routes from different protocols. Lower values are preferred. OSPF internal routes default to 10, while BGP defaults to 170, so OSPF is preferred. Administrators can override defaults using routing policies to set a different preference, allowing BGP to be preferred if desired.

Answer

The default preference for OSPF internal routes is 150, and for BGP it is 170, so OSPF is preferred.

Answer

BGP routes have a default preference of 170, which is higher than OSPF's 10, so BGP routes are preferred.

Answer

OSPF external routes have a default preference of 150, which is higher than BGP's 170.

Question 10

A network engineer is configuring a static route on a Junos device. The route must be removed from the routing table if the next-hop becomes unreachable. The engineer wants to avoid using a dynamic routing protocol. Which configuration achieves this requirement?

Accepted Answer

set routing-options static route 10.0.0.0/24 next-hop 192.168.1.1 bfd-liveness-detection minimum-interval 300. To automatically remove a static route when the next-hop becomes unreachable, you can use BFD liveness detection. BFD provides rapid failure detection and can be associated with a static route. When BFD detects a failure, the static route is withdrawn from the routing table. Other options like 'resolve' or 'no-readvertise' do not provide this functionality.

Answer

set routing-options static route 10.0.0.0/24 next-hop 192.168.1.1 no-readvertise

Answer

set routing-options static route 10.0.0.0/24 next-hop 192.168.1.1

Answer

set routing-options static route 10.0.0.0/24 next-hop 192.168.1.1 resolve

Question 11

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

Accepted Answer

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

Answer

show log messages

Answer

show configuration

Answer

show interface

Question 12

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?

Accepted Answer

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

Answer

Configure two static default routes with different metric values.

Answer

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

Answer

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

Question 13

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

Accepted Answer

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

Answer

Both routes, if they are equal-cost.

Answer

The route with the higher preference value.

Answer

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

Question 14

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

Accepted Answer

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

Answer

BGP routes

Answer

OSPF routes

Question 15

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

Accepted Answer

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

Answer

Both routes are active.

Answer

The static route because it has a lower preference.

Answer

Neither route is active.