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

Question 1

A network administrator is configuring a DMVPN Phase 3 network with OSPF. The hub router is configured with `ip nhrp redirect` and the spokes with `ip nhrp shortcut`. The administrator notices that spoke-to-spoke traffic is still going through the hub. What is the most likely reason?

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

Accepted Answer

The OSPF network type on the spokes is not set to broadcast.. In DMVPN Phase 3, NHRP redirect and shortcut require that the hub is the primary next-hop for spoke-to-spoke traffic. For OSPF, this is achieved by configuring the network type as broadcast on all routers, making the hub the DR. Spokes then have a default route or specific routes via the hub. When a spoke sends traffic to another spoke, the hub receives it, sends an NHRP redirect to the source spoke, and the source spoke initiates a shortcut tunnel. If the OSPF network type is not broadcast, the hub may not be the DR, and redirects may not be triggered properly, causing traffic to continue through the hub.

Answer

The spokes are not configured with `ip nhrp network-id`.

Answer

The hub is not configured with `ip nhrp map multicast dynamic`.

Answer

The spokes are not configured with `ip nhrp map multicast dynamic`.

Question 2

A network engineer is configuring OSPF on a router that connects to a service provider via a WAN link. The engineer wants to ensure that the router does not become a transit path for external routes learned from the service provider. Which OSPF area type should be configured on the interface connecting to the service provider?

Accepted Answer

Stub area. A stub area prevents Type 5 LSAs from entering, so the router will not learn external routes from the service provider and cannot advertise them to other routers. This reduces resource usage and prevents the router from acting as a transit path for external routes. Totally stubby is too restrictive, NSSA allows external routes, and backbone area allows all LSAs.

Answer

Backbone area (Area 0)

Answer

Not-so-stubby area (NSSA)

Answer

Totally stubby area

Question 3

A network engineer is configuring policy-based routing (PBR) on a Cisco router. The goal is to forward traffic from subnet 10.10.10.0/24 that is destined for any address to next-hop 192.168.2.2, while all other traffic should follow the routing table. Which configuration achieves this?

Accepted Answer

route-map PBR permit 10
 match ip address 10
 set ip next-hop 192.168.2.2
interface GigabitEthernet0/0
 ip policy route-map PBR
access-list 10 permit 10.10.10.0 0.0.0.255. Policy-based routing uses route maps to match traffic and set a next-hop. The correct configuration matches the source subnet with an ACL and sets the next-hop to 192.168.2.2. Applying the route map to the incoming interface ensures that traffic from that subnet is policy-routed. Other traffic follows the routing table.

Answer

route-map PBR permit 10
 match ip address 10
 set interface GigabitEthernet0/1
interface GigabitEthernet0/0
 ip policy route-map PBR
access-list 10 permit 10.10.10.0 0.0.0.255

Answer

route-map PBR permit 10
 match ip address 10
 set ip next-hop 192.168.2.2
interface GigabitEthernet0/1
 ip policy route-map PBR
access-list 10 permit 10.10.10.0 0.0.0.255

Answer

route-map PBR permit 10
 match ip address 10
 set ip default next-hop 192.168.2.2
interface GigabitEthernet0/0
 ip policy route-map PBR
access-list 10 permit 10.10.10.0 0.0.0.255

Question 4

A network engineer is configuring Policy-Based Routing (PBR) on a Cisco IOS-XE router. The engineer wants to route traffic from subnet 10.1.1.0/24 to a next-hop of 192.168.1.1, and traffic from subnet 10.2.2.0/24 to a next-hop of 192.168.2.1. Both policies should be applied to interface GigabitEthernet0/0. Which two configurations are required to accomplish this? (Choose two.)

Accepted Answer

Apply the route map to the interface using the 'ip policy route-map' command.. Policy-Based Routing requires a route map that defines match criteria (like source subnet via ACL) and set actions (like next-hop). The route map must then be applied to an interface with the 'ip policy route-map' command. These two steps are essential: without the route map, there are no policies; without applying it, the policies are not enforced. Other commands like ACLs are part of the route map but not separate required configurations.

Answer

Set the next-hop using the 'set ip next-hop' command within the route map.

Answer

Enable PBR globally using the 'ip policy routing' command in global configuration mode.

Answer

Configure ACLs to match the source subnets and reference them in the route map match statements.

Question 5

A network engineer is configuring a Cisco router to redistribute routes from OSPF into EIGRP. The OSPF routes are present in the routing table, but they are not appearing in EIGRP updates. The engineer has configured 'redistribute ospf 1 metric 10000 100 255 1 1500' under router eigrp 10. What is the most likely reason?

Accepted Answer

The OSPF routes are being redistributed but are being filtered by an EIGRP distribute-list or route-map.. When redistributing OSPF into EIGRP, the routes must be present in the routing table and not filtered by any distribute-list or route-map. The seed metric is correctly specified. A common cause for redistributed routes not appearing is an EIGRP distribute-list or route-map that denies them. Therefore, checking for such filters is the most likely solution.

Answer

The OSPF routes are not in the routing table because they are not being installed due to a distance issue.

Answer

The OSPF routes are not in the EIGRP topology table because EIGRP requires a seed metric.

Answer

The OSPF routes are not being redistributed because the 'redistribute ospf 1' command requires the 'match internal external 1 external 2' keywords to include all OSPF route types.

Question 6

A network engineer is configuring OSPFv3 on a Cisco router. The router has two interfaces: GigabitEthernet0/0 in area 0 and GigabitEthernet0/1 in area 1. The engineer wants to summarize the IPv6 addresses of GigabitEthernet0/1 into area 0 using the prefix 2001:DB8:1::/48. Which command should be used?

Accepted Answer

area 1 range 2001:DB8:1::/48. Inter-area summarization in OSPFv3 is configured with the area range command under the IPv6 router OSPF process. This command summarizes routes from the specified area into other areas. It is applied on an ABR. The other commands are used for external summarization or are not valid for this purpose.

Answer

summary-address 2001:DB8:1::/48

Answer

ipv6 ospf summary-prefix 2001:DB8:1::/48

Answer

ipv6 router ospf 1
 area 1 range 2001:DB8:1::/48

Question 7

A network engineer is configuring BGP on a Cisco IOS router. The engineer wants to ensure that the router prefers a route learned from a specific eBGP neighbor over other eBGP routes. Which BGP attribute should be manipulated to achieve this?

Accepted Answer

Weight. Weight is a Cisco-proprietary BGP attribute that is local to the router and is the first attribute evaluated in the BGP best path selection algorithm. By assigning a higher weight to routes learned from a specific eBGP neighbor, the router will prefer those routes. Weight is not advertised to any BGP peer, so it only affects the local router's decision. This makes it ideal for the scenario described.

Answer

Multi-Exit Discriminator (MED)

Answer

AS Path

Answer

Local Preference

Question 8

A network engineer is configuring OSPFv3 on a dual-stack router. The router must form an adjacency with a neighboring router over an interface that is also running IPv4 OSPFv2. The engineer wants to minimize configuration and ensure that OSPFv3 uses the same link-local addresses as IPv6. Which command should be used to enable OSPFv3 on the interface?

Accepted Answer

ipv6 ospf 1 area 0. OSPFv3 is enabled on an interface using the interface-level command 'ipv6 ospf process-id area area-id'. This command activates OSPFv3 on the interface and uses the link-local address for neighbor communication, which is the default and requires no additional configuration. It allows OSPFv3 to run independently of OSPFv2 for IPv4 on the same interface.

Answer

ipv6 router ospf 1

Answer

router ospfv3 1

Answer

ospfv3 1 ipv6 area 0

Question 9

A network engineer is configuring a DMVPN Phase 3 hub-and-spoke topology using mGRE and NHRP. The engineer wants to enable direct spoke-to-spoke communication. Which two configurations are required to achieve this? (Choose two.)

Accepted Answer

Enable NHRP redirect on the hub.. In DMVPN Phase 3, the hub must act as an NHS to maintain NHRP mappings, and NHRP redirect must be enabled on the hub to inform spokes of a better direct path. NHRP shortcut on spokes is also used but is not one of the two required configurations; the hub's redirect triggers the shortcut. Static mappings and static routes are not required.

Answer

Configure the spokes with a static NHRP mapping to each other.

Answer

Enable NHRP shortcut on the spokes.

Answer

Configure the hub with a static route to each spoke's tunnel IP.

Question 10

A network administrator is troubleshooting an EIGRP adjacency that is not forming between two routers. The routers are directly connected via a point-to-point serial link. The administrator verifies that the interfaces are up and IP connectivity is working. Which of the following could be a reason for the EIGRP adjacency failure?

Accepted Answer

The K-values are mismatched.. EIGRP adjacency formation requires matching autonomous system numbers, K-values, and authentication (if configured). Mismatched K-values will prevent adjacency because the metric calculation would be inconsistent. Mismatched AS numbers also prevent adjacency, but the question asks for a possible reason, and K-values is a correct and specific answer. The other options are either not always required (hello timers) or not necessarily the case (passive interface).

Answer

The hello timer intervals are mismatched.

Answer

The interface is configured as passive.

Answer

The EIGRP autonomous system numbers are mismatched.

Question 11

A network administrator is troubleshooting an EIGRP adjacency that is not forming between two routers. The routers are directly connected via a GigabitEthernet link. The administrator verifies that the interfaces are up and IP addresses are correctly configured. The output of 'show ip eigrp neighbors' on one router shows no neighbors. Which of the following is the most likely cause?

Accepted Answer

The EIGRP autonomous system numbers do not match.. For EIGRP neighbors to form, the autonomous system number must match on both routers. If the AS numbers differ, the routers will not process each other's hello packets, and no adjacency will be established. Other factors like K-values, timers, and passive interfaces can also prevent adjacency, but the AS number mismatch is the most fundamental and common cause when basic connectivity is verified.

Answer

The K-values do not match.

Answer

The hello timer intervals are different.

Answer

The interface is configured as passive.

Question 12

A network engineer is troubleshooting an MPLS Layer 3 VPN. The engineer notices that the provider edge (PE) router is not receiving VPNv4 routes from a remote PE. Which two statements are true regarding the requirements for VPNv4 route exchange? (Choose two.)

Accepted Answer

The PE routers must have a full mesh of iBGP sessions or use route reflectors.. VPNv4 route exchange in MPLS L3VPN requires that PE routers have iBGP sessions, either full mesh or via route reflectors, to exchange VPNv4 routes. Additionally, MPLS LDP must be enabled on core-facing interfaces to establish label switched paths for forwarding VPN traffic. Without these, VPNv4 routes cannot be exchanged or forwarded properly.

Answer

The PE routers must use the same BGP autonomous system number.

Answer

The PE routers must be directly connected.

Answer

The PE routers must have a route distinguisher configured for each VRF.

Question 13

A network engineer is configuring a GRE tunnel between two Cisco routers. The tunnel will carry OSPF traffic. Which two statements are true regarding the configuration and operation of this tunnel? (Choose two.)

Accepted Answer

The tunnel can be configured with a keepalive to detect remote end failures.. GRE tunnels require that the source and destination addresses are reachable via the underlay network for the tunnel to come up. Keepalives can be configured to monitor the remote end. The other statements are not universally true: an IP address is not mandatory for the tunnel itself, OSPF may need additional configuration, and the tunnel MTU does not have to match the physical interface MTU.

Answer

The tunnel interface must have an IP address configured.

Answer

The tunnel interface must be configured with the same MTU as the physical interface.

Answer

OSPF can form an adjacency over the tunnel without any additional configuration.

Question 14

A network engineer is implementing policy-based routing (PBR) on a Cisco IOS router. The engineer wants to route traffic from a specific subnet to a next-hop IP address that is not directly connected, and also wants to mark the traffic with a specific DSCP value. Which two actions must be configured to achieve this? (Choose two.)

Accepted Answer

Apply the route map to the incoming interface using the 'ip policy route-map' command.. To implement PBR, you must create a route map that defines match criteria (such as source subnet) and set actions (such as next-hop IP and DSCP marking). Then, you must apply the route map to the incoming interface using the 'ip policy route-map' command. These two steps are essential for PBR to take effect. Other steps like ensuring CEF is enabled or having a route to the next-hop are prerequisites but not the core configuration actions.

Answer

Configure a static route for the next-hop IP address.

Answer

Set the DSCP value within the route map using the 'set ip dscp' command.

Answer

Enable CEF on the router.

Question 15

A network engineer is troubleshooting a multi-area OSPFv2 network. Area 10 is a totally stubby area connected to Area 0 via an ABR. A router in Area 10 is not receiving any external routes. The engineer verifies that the ABR has the 'area 10 stub no-summary' command configured. However, the router in Area 10 still has no default route. What is the most likely cause?

Accepted Answer

The router in Area 10 is not configured with the 'area 10 stub' command, so it cannot process the default route.. In a totally stubby area, the ABR automatically injects a default route into the area, but all routers in that area must be configured as stub routers. Without the 'area 10 stub' command on the internal router, it will not form adjacencies with the ABR and will not receive the default route. The ABR's configuration is correct, but the internal router's configuration is incomplete.

Answer

The ABR is not configured to generate a default route because the 'default-information originate' command is missing.

Answer

The router in Area 10 is configured as a stub router and cannot accept Type 3 LSAs.

Answer

The ABR is not generating a default route because it lacks a matching external route in its routing table.