300-410 Layer 3 Technologies Practice Test 7 — 15 Questions

Question 1

A network engineer is troubleshooting an OSPF adjacency between two routers on a broadcast Ethernet segment. Router R1 is configured with the ip ospf priority 0 command on its GigabitEthernet0/0 interface. Router R2 has default priority. The engineer observes that the adjacency remains in the 2-WAY state and no DR/BDR election occurs. Which action resolves this issue?

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

Accepted Answer

Set the OSPF priority on R1 to a non-zero value.. The 2-WAY state on a broadcast segment typically indicates that DR/BDR election has completed but the routers are not forming a full adjacency because they are not DR or BDR. When a router has priority 0, it is ineligible to become DR or BDR. If all routers on the segment have priority 0, no DR is elected, and the adjacency remains in 2-WAY. Setting a non-zero priority on at least one router allows the election to proceed and the adjacency to reach FULL.

Answer

Change the OSPF network type to point-to-point on both routers.

Answer

Clear the OSPF process on both routers to force a new election.

Answer

Configure a static neighbor statement on R1 for R2's router ID.

Question 2

A network engineer is configuring OSPFv3 on a router that connects to an IPv6-only segment. The router must establish an OSPFv3 adjacency with a neighboring router over a link where the global unicast addresses are not reachable. Which command is required to enable OSPFv3 on the interface and allow the adjacency to form?

Accepted Answer

ipv6 ospf 1 area 0. To enable OSPFv3 on an interface, the interface-level command ipv6 ospf process-id area area-id must be configured. OSPFv3 uses link-local addresses for neighbor communication, so global unicast reachability is not required. The router configuration mode command ipv6 router ospf only defines the process; it does not activate OSPFv3 on interfaces. The ospfv3 command is valid but is typically used for multi-AF scenarios. The command without a process ID is invalid.

Answer

ipv6 ospf area 0

Answer

ospfv3 1 ipv6 area 0

Answer

ipv6 router ospf 1

Question 3

A network engineer is troubleshooting an EIGRP adjacency issue between two routers. The routers are directly connected via Gigabit Ethernet. The engineer notices that the adjacency is stuck in the EXSTART state. Which of the following is the most likely cause?

Accepted Answer

Mismatched MTU sizes on the interfaces. The EXSTART state in EIGRP is where routers negotiate the master/slave relationship and exchange sequence numbers. A mismatch in MTU sizes prevents this negotiation because the routers cannot agree on the maximum packet size. Therefore, the adjacency remains in EXSTART until the MTU mismatch is resolved.

Answer

Mismatched EIGRP autonomous system numbers

Answer

Mismatched hello and hold timers

Answer

Mismatched K values

Question 4

A network engineer is troubleshooting an EIGRP adjacency that is stuck in the ACTIVE state. The engineer suspects a mismatch in EIGRP parameters. Which two parameters must match for an EIGRP adjacency to form and remain stable? (Choose two.)

Accepted Answer

Autonomous system number. For an EIGRP adjacency to form, the autonomous system number and K values must match on both routers. The AS number identifies the EIGRP domain, and mismatched AS numbers prevent neighbor relationships. K values affect metric calculation, and a mismatch causes EIGRP to reject hellos. Hello interval, router ID, and authentication key are not mandatory matching parameters unless authentication is enabled, but even then, the key must match only if authentication is configured on both sides.

Answer

Hello interval

Answer

Router ID

Answer

Authentication key

Question 5

A network engineer is troubleshooting a DMVPN Phase 3 network using OSPF. The hub router is not receiving routes from a spoke router. The engineer verifies that the tunnel interface is up and IPsec is working. Which two actions should the engineer take to allow OSPF to form an adjacency over the DMVPN tunnel? (Choose two.)

Accepted Answer

Ensure that the OSPF hello and dead timers match on all routers.. In a DMVPN Phase 3 network, OSPF adjacency issues often stem from incorrect network type or mismatched timers. The point-to-multipoint network type is recommended because it avoids DR/BDR election and allows direct adjacencies. Additionally, OSPF hello and dead timers must match on all routers. These two actions are critical to establish OSPF neighbor relationships over the DMVPN tunnel.

Answer

Configure the tunnel interface as OSPF network type broadcast.

Answer

Enable OSPF demand circuits on the tunnel interfaces.

Answer

Set the OSPF priority to 0 on all spoke routers.

Question 6

A network administrator is configuring a GRE tunnel between two Cisco routers. The tunnel source is a loopback interface, and the tunnel destination is a loopback interface on the remote router. The administrator notices that the tunnel interface is up, but no traffic is passing through. What is the most likely cause?

Accepted Answer

There is no route to the networks on the other side of the tunnel.. When a GRE tunnel interface is up, it means the tunnel source and destination are reachable. However, for traffic to pass through the tunnel, there must be routes to the networks reachable via the tunnel. Without such routes, packets destined for those networks will not be sent into the tunnel. The tunnel interface being up does not automatically create routes. Therefore, the most likely cause is the absence of routes to the remote networks.

Answer

The tunnel source and destination are not properly routed.

Answer

The tunnel IP addresses are in different subnets.

Answer

The tunnel destination is not reachable.

Question 7

A network administrator is troubleshooting an EIGRP adjacency that is stuck in the ACTIVE state. The router has sent queries to its neighbors but has not received all replies. Which action should the administrator take to resolve this issue while minimizing network disruption?

Accepted Answer

Implement EIGRP stub routing on remote routers to limit query propagation.. EIGRP stuck-in-active (SIA) occurs when a router does not receive all replies to its queries within the active timer. The most effective way to prevent SIA is to limit query propagation using EIGRP stub routing on routers that should not be transit paths. This reduces the query domain and ensures that remote routers do not receive queries for routes they cannot reach, thus preventing the SIA condition.

Answer

Manually clear the EIGRP neighbor relationship with the clear ip eigrp neighbors command.

Answer

Increase the EIGRP query timeout using the timers active-time command.

Answer

Configure EIGRP stub routing on the neighbor that is not replying.

Question 8

A network administrator is troubleshooting an EIGRP adjacency that is stuck in the ACTIVE state. The router is running EIGRP AS 100 and has a single feasible successor for the destination network 10.1.1.0/24. The administrator issues the show ip eigrp topology command and sees that the feasible successor has a reported distance of 1500 and a feasible distance of 2000. The successor has a feasible distance of 1800. What is the most likely cause of the stuck-in-ACTIVE state?

Accepted Answer

The router has lost its successor and is querying neighbors for a new path, but no neighbor has replied.. EIGRP routes go into ACTIVE state when the successor is lost and there is no feasible successor. The feasibility condition requires that a neighbor's reported distance be less than the current feasible distance. In this scenario, the feasible successor meets that condition, so the router should have a feasible successor. If the route is stuck ACTIVE, it is likely because the router is querying neighbors and not receiving replies, possibly due to a broken neighbor relationship or filtering.

Answer

The feasible successor's feasible distance is greater than the successor's feasible distance.

Answer

The feasible successor's reported distance is greater than the successor's feasible distance.

Answer

The feasible successor's reported distance is less than the successor's feasible distance, so the router should have a feasible successor and not go ACTIVE.

Question 9

A network administrator is configuring a GRE tunnel between two Cisco routers. The tunnel interface is configured with the tunnel mode gre ip command. The administrator wants to ensure that the tunnel can carry multicast traffic. Which additional configuration is required?

Accepted Answer

No additional configuration is required; GRE supports multicast by default.. GRE tunnels with tunnel mode gre ip inherently support multicast traffic. The tunnel interface will forward multicast packets without requiring extra configuration. Therefore, no additional commands are needed to enable multicast support on the tunnel.

Answer

Enable PIM sparse-mode on the tunnel interface.

Answer

Enable the tunnel interface with the ip multicast-routing command.

Answer

Configure the tunnel source interface with the ip pim sparse-mode command.

Question 10

A network engineer is configuring a Cisco IOS router to support VRF-lite. The router has two VRFs: VRF-A and VRF-B. The engineer wants to enable OSPFv2 in each VRF and ensure that routes from VRF-A are not leaked into VRF-B. Which configuration is correct?

Accepted Answer

router ospf 1 vrf VRF-A
 network 10.1.1.0 0.0.0.255 area 0
router ospf 2 vrf VRF-B
 network 10.2.2.0 0.0.0.255 area 0. In VRF-lite, each VRF maintains its own routing table. To run OSPFv2 per VRF, you must create separate OSPF processes and bind each to a VRF using the vrf keyword. This ensures that routes are isolated. The network statements then advertise the subnets within the context of that VRF. Using separate process IDs is mandatory because a process ID can only be associated with one VRF.

Answer

router ospf 1 vrf VRF-A
 network 10.1.1.0 0.0.0.255 area 0
router ospf 1 vrf VRF-B
 network 10.2.2.0 0.0.0.255 area 0

Answer

router ospf 1
 network 10.1.1.0 0.0.0.255 area 0
 network 10.2.2.0 0.0.0.255 area 0
 vrf VRF-A
 vrf VRF-B

Answer

router ospf 1
 network 10.1.1.0 0.0.0.255 area 0
router ospf 2
 network 10.2.2.0 0.0.0.255 area 0
ip vrf VRF-A
ip vrf VRF-B

Question 11

A network engineer is troubleshooting a BGP neighbor relationship that is stuck in the Active state. The engineer has verified that IP connectivity exists between the two routers, and that the BGP configurations are correct. Which two actions could resolve the issue? (Choose two.)

Accepted Answer

Verify that the neighbor's update-source is configured correctly.. BGP neighbor stuck in Active state indicates a failure in TCP session establishment. Common causes include incorrect update-source configuration, which prevents the router from using a reachable source IP, and ACLs blocking TCP port 179. Both must be verified to resolve the issue. Other factors like router ID or AS number are important but typically cause different symptoms or occur after TCP is established.

Answer

Verify that the eBGP multihop command is configured if the neighbor is multiple hops away.

Answer

Ensure that the BGP router ID is unique.

Answer

Confirm that the neighbor's autonomous system number is correct.

Question 12

A network engineer is troubleshooting an OSPF adjacency between two routers on a broadcast Ethernet segment. Router R1 is configured with the ip ospf priority 0 command on its GigabitEthernet0/0 interface. Router R2 has default priority. The engineer observes that the adjacency remains in the 2-WAY state and no DR/BDR election occurs. Which action resolves this issue?

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

Accepted Answer

The PE routers are not configured with `address-family vpnv4` under the BGP process.. In MPLS L3VPN, customer routes are carried in the VPNv4 address family of MP-BGP. If the VPNv4 address family is not activated for the BGP neighbors, the customer routes will not be advertised between PE routers. The BGP session may still be established for IPv4 unicast, but that does not carry VPNv4 routes. Therefore, the most likely cause is the missing `address-family vpnv4` configuration.

Answer

The PE routers are not configured with `mpls ldp router-id`.

Answer

The PE routers are not configured with `neighbor x.x.x.x activate` under the IPv4 unicast address family.

Answer

The PE routers are not configured with `route-target export` in the VRF.

Question 13

A network engineer is configuring EIGRP on a Cisco IOS XE router. The router has two paths to a remote network: one via a 100 Mbps link and another via a 10 Mbps link. The engineer wants EIGRP to use the 100 Mbps link as the primary path and the 10 Mbps link as a backup only if the primary fails. Which EIGRP feature should the engineer configure to achieve this?

Accepted Answer

Configure the 10 Mbps link as a feasible successor by ensuring it meets the feasibility condition.. EIGRP uses the concept of a successor (primary route) and feasible successor (backup route). The feasible successor is a loop-free backup that is installed in the topology table and used if the successor fails. To make the 10 Mbps link a backup, it must meet the feasibility condition, which ensures it is loop-free. The 100 Mbps link will be the successor due to its better metric, and the 10 Mbps link will be the feasible successor.

Answer

Adjust the EIGRP metric weights using the `metric weights` command.

Answer

Set the administrative distance of the 10 Mbps link to a higher value than the 100 Mbps link.

Answer

Configure EIGRP variance to allow unequal-cost load balancing.

Question 14

A network engineer is configuring a Cisco IOS-XE router for MPLS Layer 3 VPN. The engineer wants to ensure that the router can forward MPLS packets received from a core-facing interface to a CE-facing interface. The router is a PE router. Which configuration is required to enable this forwarding?

Accepted Answer

Configure a VRF and assign the CE-facing interface to it, and enable MPLS on the core-facing interface.. For a PE router to forward MPLS packets from the core to a CE-facing interface, it must have a VRF configured and the CE-facing interface assigned to that VRF. Additionally, MPLS must be enabled on the core-facing interface to receive MPLS packets. This allows the router to perform label lookup and forward the packet out the correct VRF interface.

Answer

Enable MPLS on the core-facing interface with the mpls ip command.

Answer

Enable MPLS LDP on the CE-facing interface.

Answer

Configure a route target on the CE-facing interface.

Question 15

A network engineer is configuring policy-based routing (PBR) on a Cisco IOS XE router. The goal is to route traffic from a specific subnet to a next-hop IP address that is not directly connected. The engineer uses a route map with a `set ip next-hop` statement. Which two statements are true regarding this configuration? (Choose two.)

Accepted Answer

The next-hop IP address must be reachable via a route in the routing table.. Two statements are correct: the next-hop IP address must be reachable via a route in the routing table, and PBR is applied to an interface using the `ip policy route-map` command. When using `set ip next-hop` with a non-directly connected next hop, the router must have a route to that next hop; otherwise, the policy is bypassed. Also, applying the route map to the interface is essential for PBR to take effect on transit traffic.

Answer

If the next-hop is not reachable, the packet is dropped by default.

Answer

PBR takes precedence over the routing table only for packets that are generated locally by the router.

Answer

The `set ip next-hop` command can only specify directly connected next hops.