300-410 Layer 3 Technologies Practice Test 14 — 15 Questions

Question 1

A network administrator is troubleshooting a DMVPN Phase 3 network using OSPF as the routing protocol. Spoke routers are not learning routes from other spokes. Which two actions should be taken to resolve this issue? (Choose two.)

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

Accepted Answer

Configure the spoke routers with 'ip nhrp shortcut' on their tunnel interfaces.. In DMVPN Phase 3, spoke-to-spoke communication requires the hub to send NHRP redirect messages and the spokes to support NHRP shortcuts. The hub must have 'ip nhrp redirect' configured, and each spoke must have 'ip nhrp shortcut' configured. These commands enable the spokes to dynamically discover and establish direct tunnels to other spokes, bypassing the hub. Without them, spokes will not learn the specific routes to other spokes and will continue to route traffic through the hub, which is inefficient.

Answer

Configure the hub as a route reflector for BGP.

Answer

Disable split horizon on the hub's tunnel interface.

Answer

Change the OSPF network type to point-to-multipoint on all routers.

Question 2

A network technician is configuring a Cisco router to forward traffic to a remote network. The technician enters the command 'ip route 172.16.0.0 255.255.0.0 10.0.0.1'. However, the router does not install the route in its routing table. What is the most likely reason?

Accepted Answer

The next-hop address 10.0.0.1 is not reachable.. A static route is only installed in the routing table if its next-hop address is reachable. If the next-hop 10.0.0.1 is not reachable (e.g., no route to it, or interface down), the route will not be installed. The default administrative distance is low, the mask is correct, and the 'permanent' keyword is not required for installation. Therefore, the most likely cause is an unreachable next-hop.

Answer

The administrative distance of the static route is too high.

Answer

The subnet mask is incorrect.

Answer

The static route is missing the 'permanent' keyword.

Question 3

A network engineer is configuring a GRE tunnel between two routers. The tunnel interface is up, but OSPF neighbors are not forming. The engineer suspects a Layer 3 issue. Which command should be used to verify that the tunnel endpoints are reachable?

Accepted Answer

ping <remote tunnel endpoint IP>. To verify that the tunnel endpoints are reachable, the engineer should ping the remote tunnel endpoint IP address. This tests the underlay network connectivity, which is required for the GRE tunnel to carry traffic. If the ping fails, the tunnel will not pass traffic even if the tunnel interface is up. Other commands like show ip interface brief only show interface status, show ip ospf neighbor shows adjacency state, and traceroute is more for path analysis. The ping is the most direct and effective method.

Answer

show ip interface brief

Answer

traceroute <remote tunnel endpoint IP>

Answer

show ip ospf neighbor

Question 4

A network engineer is configuring a Cisco router to authenticate OSPF neighbors using MD5. The router is connected to two OSPF neighbors on the same subnet. The engineer wants to enable MD5 authentication on the interface with a key ID of 1 and a password of 'Cisco123'. Which command sequence correctly accomplishes this?

Accepted Answer

interface GigabitEthernet0/0
 ip ospf authentication message-digest
 ip ospf message-digest-key 1 md5 Cisco123. To enable OSPF MD5 authentication on a specific interface, you must enter interface configuration mode and issue both 'ip ospf authentication message-digest' to turn on MD5 authentication and 'ip ospf message-digest-key 1 md5 Cisco123' to define the key. This method allows per-interface authentication, which is suitable when only certain interfaces require MD5. The other options either misplace the key command, use plaintext authentication, or configure area-wide authentication incorrectly.

Answer

router ospf 1
 area 0 authentication
 ip ospf message-digest-key 1 md5 Cisco123

Answer

router ospf 1
 area 0 authentication message-digest
 ip ospf message-digest-key 1 md5 Cisco123

Answer

interface GigabitEthernet0/0
 ip ospf authentication-key Cisco123
 ip ospf authentication message-digest

Question 5

A network technician is configuring a Cisco IOS router to authenticate OSPFv2 neighbors using MD5. The technician enters the following commands:

interface GigabitEthernet0/0
 ip ospf authentication message-digest
 ip ospf message-digest-key 1 md5 cisco

After applying the configuration, the router does not form an adjacency with its neighbor. What is the most likely reason?

Accepted Answer

The neighbor router is not configured with the same MD5 key ID and key string.. OSPF MD5 authentication requires that both neighbors use the same key ID and key string. When the technician configures MD5 on one router but the neighbor has not been configured with the identical key, the MD5 digest in OSPF hellos will not match, and the routers will not form an adjacency. The technician should verify the neighbor's configuration and ensure both key ID and key string match exactly.

Answer

The key string must be encrypted using the 'service password-encryption' command.

Answer

The 'ip ospf authentication message-digest' command must be configured globally, not on the interface.

Answer

The key ID must be the same on both routers, but the key string can differ.

Question 6

A network engineer is troubleshooting a DMVPN Phase 3 deployment on a Cisco IOS XE router. The hub router is configured with 'ip nhrp redirect' and the spoke routers with 'ip nhrp shortcut'. However, spoke-to-spoke traffic is still traversing the hub. Which action should the engineer take to enable direct spoke-to-spoke communication?

Accepted Answer

Ensure that the spoke routers have a route to the spoke networks via the tunnel interface and that NHRP resolution is working.. Spoke-to-spoke shortcuts in DMVPN Phase 3 require that spokes have a route to the destination network via the tunnel interface and that NHRP resolution succeeds. The hub uses NHRP redirect to tell the spoke that a better path exists, and the spoke uses NHRP shortcut to install a direct entry. Without these, traffic continues through the hub.

Answer

Configure 'ip nhrp network-id' with the same value on all routers.

Answer

Configure 'ip nhrp map multicast dynamic' on the hub.

Answer

Enable 'ip nhrp authentication' on all routers.

Question 7

A network engineer is configuring EIGRP on a router. The engineer wants to ensure that the router does not send EIGRP updates out of an interface connected to a non-EIGRP neighbor, but still advertises the connected network into EIGRP. Which configuration command should be used?

Accepted Answer

passive-interface <interface> under router EIGRP configuration. The passive-interface command under EIGRP configuration stops EIGRP from sending hellos and updates on the specified interface, preventing adjacency formation with non-EIGRP neighbors. Meanwhile, the connected network is still advertised into EIGRP if it falls under a network statement. Other options either do not prevent updates or also stop advertisement of the network.

Answer

no network <network> under router EIGRP configuration

Answer

distribute-list out under router EIGRP configuration

Answer

ip split-horizon under interface configuration

Question 8

A network engineer is implementing MPLS Layer 3 VPNs. The engineer wants to ensure that customer routes are propagated across the MPLS core. Which protocol is typically used within the provider core to distribute VPNv4 routes?

Accepted Answer

BGP. In MPLS Layer 3 VPNs, Multiprotocol BGP (MP-BGP) is used to distribute VPNv4 routes between provider edge routers. MP-BGP carries the VPNv4 address family, which includes the route distinguisher and route target extended communities, along with MPLS labels. This allows the provider core to forward customer traffic based on labels.

Answer

OSPF

Answer

LDP

Answer

EIGRP

Question 9

A network engineer is configuring policy-based routing (PBR) on a Cisco IOS router. The engineer wants traffic from a specific subnet to be routed via a next-hop IP address that is not directly connected. Which command is required under the route-map configuration?

Accepted Answer

set ip next-hop recursive 10.1.1.1. PBR with a non-directly connected next-hop requires the 'set ip next-hop recursive' command. This allows the router to recursively look up the next-hop in the routing table to find a directly connected next-hop. Without the 'recursive' keyword, the router expects the next-hop to be directly connected and will not install the policy route if it is not.

Answer

set ip next-hop 10.1.1.1

Answer

set interface GigabitEthernet0/1

Answer

set ip default next-hop 10.1.1.1

Question 10

A network administrator is configuring EIGRP on a router and wants to ensure that only a specific subnet is advertised out of an interface. The router has the following configuration: 'router eigrp 100', 'network 10.0.0.0', 'passive-interface GigabitEthernet0/0'. The administrator wants to advertise 10.1.1.0/24 out of GigabitEthernet0/0 while preventing other subnets from being advertised. Which configuration achieves this?

Accepted Answer

Remove the passive-interface command and configure a distribute-list outbound on GigabitEthernet0/0 to permit only 10.1.1.0/24.. To advertise a specific subnet out of an interface while suppressing others, the interface must not be passive so that EIGRP can form adjacencies and send updates. Then, an outbound distribute-list can filter the advertised routes, permitting only the desired subnet. This approach gives granular control over which routes are sent out of the interface, meeting the administrator's requirement.

Answer

Keep the passive-interface command and configure a distribute-list outbound on GigabitEthernet0/0 to permit only 10.1.1.0/24.

Answer

Remove the passive-interface command and configure a distribute-list inbound on GigabitEthernet0/0 to permit only 10.1.1.0/24.

Answer

Remove the passive-interface command and configure 'network 10.1.1.0 0.0.0.255' under router EIGRP.

Question 11

A network architect is designing a BGP routing policy to influence inbound traffic from an ISP. The architect wants to make a specific prefix less preferred by the ISP by prepending the AS path multiple times. Which BGP attribute should be manipulated to achieve this?

Accepted Answer

AS_PATH. AS_PATH prepending is a technique where the local AS number is added multiple times to the AS_PATH attribute of a route advertised to external peers. This increases the path length, making the route less attractive to the receiving ISP, as BGP prefers shorter AS paths. This is a standard method for influencing inbound traffic in a multi-homed environment.

Answer

LOCAL_PREF

Answer

MED

Answer

NEXT_HOP

Question 12

A network engineer is configuring OSPF on a router. The router has an interface with IP address 10.1.1.1/24 and another interface with IP address 192.168.1.1/24. The engineer wants to enable OSPF on both interfaces using a single network command under router ospf 1. Which command accomplishes this?

Accepted Answer

network 0.0.0.0 255.255.255.255 area 0. The network command in OSPF uses a wildcard mask to match interface IP addresses. To enable OSPF on all interfaces with one command, use network 0.0.0.0 255.255.255.255 area 0, which matches any IP address. This activates OSPF on both the 10.1.1.1/24 and 192.168.1.1/24 interfaces, satisfying the requirement.

Answer

network 10.0.0.0 0.255.255.255 area 0

Answer

network 10.1.1.0 0.0.0.255 area 0 and network 192.168.1.0 0.0.0.255 area 0

Answer

network 10.1.1.0 0.0.0.255 area 0

Question 13

A network administrator is configuring MPLS Layer 3 VPN on a Cisco IOS XE router. The router is a PE device connected to two CE routers in different VRFs. The administrator wants to prevent routes from one VRF from being leaked into another VRF. Which configuration step is essential to maintain VRF separation?

Accepted Answer

Configure route targets (RTs) for import and export on each VRF.. In MPLS Layer 3 VPN, VRF separation is achieved through the use of route targets (RTs). Each VRF is configured with import and export RTs. When a route is exported from a VRF, it is tagged with the export RT. The receiving PE imports the route into a VRF only if the route's RT matches the VRF's import RT. Therefore, to prevent leaking, each VRF must have unique RTs that are not shared with other VRFs.

Answer

Enable OSPF as the PE-CE routing protocol and use different process IDs.

Answer

Assign a unique route distinguisher (RD) to each VRF.

Answer

Configure BGP neighbor statements with different autonomous system numbers.

Question 14

A network engineer is implementing policy-based routing (PBR) on a Cisco router. The goal is to forward traffic from a specific source subnet to a next-hop that is not the default gateway. The engineer configures a route map with a match statement for the source subnet and a set statement for the next-hop. However, the traffic is still following the default route. What is the most likely reason?

Accepted Answer

The ip policy route-map command is not configured on the ingress interface.. Policy-based routing requires the route map to be applied to the ingress interface with the ip policy route-map command. Without this command, the route map is not evaluated, and traffic is forwarded using the normal routing table, which explains why traffic follows the default route. Other issues, such as an incorrect next-hop or missing permit statement, would cause different symptoms, such as traffic being dropped or sent to the wrong next-hop, but not reverting to the default route.

Answer

The set statement is using an incorrect next-hop address.

Answer

The route map is missing a permit statement.

Answer

The route map is not applied to the correct interface.

Question 15

A network engineer is configuring OSPF on a router that connects to a broadcast Ethernet segment. The router is connected to a switch that also connects to three other OSPF routers. The engineer wants to ensure that this router does not become the Designated Router (DR) or Backup Designated Router (BDR) on this segment, but still participates in OSPF. Which configuration should the engineer apply on the router's interface?

Accepted Answer

ip ospf priority 0. The OSPF priority value is used in the DR/BDR election on broadcast and non-broadcast multi-access segments. A priority of 0 makes the router ineligible to become DR or BDR, while still allowing it to form adjacencies and exchange routing information. This is the correct way to keep a router as a DROTHER on a segment where it should not take on a primary role.

Answer

ip ospf database-filter all out

Answer

ip ospf priority 255

Answer

ip ospf network point-to-point