Nokia 4A0-112 Exam Questions Instant Access

Question 1

Refer to the exhibit.

In the diagram, all routers are using IS-IS as their routing protocol. The number next to each link is its metric value.

What path will traffic follow from router R6 to router R3, and from router R3 to router R6?

ARouter R6 to router R3 will follow (R6-R5-R2-R3). Router R3 to router R6 will follow (R3-R2-R5-R6).

BRouter R6 to router R3 will follow (R6-R5-R2-R3). Router R3 to router R6 will follow (R3-R4-R2-R5-R6).

CRouter R6 to router R3 will follow (R6-R5-R2-R3). Router R3 to router R6 will follow (R3-R4-R7-R5-R6).

DRouter R6 to router R3 will follow (R6-R5-R7-R4-R3). Router R3 to router R6 will follow (R3-R4-R7-R5-R6).

Answer : A

The metric values between the routers dictate the routing paths, and IS-IS will calculate the shortest path based on these values.

R6 to R3: The path from R6 to R3 will go through R5 and R2, as this route has the least cumulative metric (10 + 10 + 15 = 35).

R3 to R6: The reverse path from R3 to R6 will follow R3 R2 R5 R6 because this route is also the shortest with a total metric of 10 + 10 + 10 = 30.

Question 2

Refer to the exhibit.

A static route has been configured on router R1 to reach the PC at 139.120.121.2.

What might be causing the ping to fail?

ARouter R2 needs a static route to the PC.

BRouter R1 needs a static route to router R2.

CThe configured next hop does not belong to a subnet adjacent to R1.

DThe configured static route needs to be a default route.

Answer : C

In the configuration on router R1, the static route is defined with the next-hop IP address of 139.120.121.1.

However, the next-hop IP address 139.120.121.1 does not belong to the same subnet as the directly connected interface on R1, which is 172.31.1.1/30. For the static route to work properly, the next-hop IP address must be reachable via a directly connected interface, meaning it must be within the same subnet.

Therefore, this mismatch in subnet adjacency is likely causing the failure to reach the destination (139.120.121.2).

Question 3

On a broadcast interface, an IS-IS router receives an LSP that is newer than the one on its database. Which of the following statements best describes the actions taken by the router as a consequence?

AThe router sends back a copy of the LSP from its database to its neighbor.

BThe router updates its database with the LSP and floods a copy to its neighbors on other interfaces.

CThe router updated its database with the LSP, acknowledges the LSP with a PSNP, and floods a copy to its neighbors on other interfaces.

DThe router updates its database with the LSP and acknowledges it with a PSNP.

Answer : C

When an IS-IS router receives a newer LSP (Link-State PDU) than the one already in its database, it takes the following actions:

Updates its link-state database with the new LSP.

Acknowledges the LSP with a PSNP (Partial Sequence Number PDU), which is sent to the router that originated the LSP, confirming the receipt of the newer LSP.

Floods a copy of the updated LSP to its neighbors on other interfaces to ensure all routers in the network have the updated topology information.

Question 4

Refer to the exhibit.

Routers R1 through R4 are running an IGP in such a way that they have each other's system IP addresses in their routing tables. A static route is configured on router R1 so that it can reach subnetwork 10.4.100.0/24. The network administrator decides to use an indirect static route, as shown in the diagram. However, pinging the server from router R1 fails. What may be the problem in this case?

ARouter R1 drops the echo request because address 10.10.10.3 does not belong to an adjacent router.

BRouter R2 drops the echo request because it does not have subnet 10.4.100.0/24 in its routing table.

CRouter R3 drops the echo request because it does not have subnet 10.4.100.0/24 in its routing table.

DThe echo request arrives at the server but there is no path for the echo response to return to router R1.

Answer : D

The static route configured on router R1 uses an indirect next-hop, which is 10.10.10.3 (R3). While the echo request from R1 reaches the server through the IGP, the problem lies in the return path for the echo response.

The route 10.4.100.0/24 is reachable through R3, but there is no reciprocal route in R3's routing table that allows the response to flow back towards R1. This results in a failure to return the echo response to R1, causing the ping to fail.

Question 5

Two IS-IS neighboring routers are trying to establish an adjacency, but the interface has been configured as broadcast on one of them and as point-to-point on the other. Why is the adjacency not established?

AThe routers do not agree on the result of the DIS election.

BThe routers discard the received Hello messages because they are not the expected type: LAN Hello vs point-to-point Hello.

CThe routers do not receive each other's Hello messages because they listen for messages transmitted to different multicast MAC addresses.

DThe routers do not receive each other's Hello messages because they listen for messages transmitted to different multicast IP addresses.

Answer : B

IS-IS routers use different types of Hello messages depending on whether the interface is configured as a broadcast (LAN) or point-to-point (P2P) link.

On a broadcast network (e.g., Ethernet), IS-IS routers use LAN Hello packets to establish adjacencies.

On a point-to-point link, IS-IS uses point-to-point Hello packets.

If one router is configured for a broadcast interface and the other for point-to-point, they will exchange incompatible Hello packets, and as a result, neither router will accept the other's Hello messages, preventing the adjacency from being established.

Question 6

Refer to the exhibit.

In the IS-IS network shown, router R1 has been configured to summarize subnetworks 20.20.1.0/24 and 20.20.2.0/24 as 20.20.0.0/16. Which routers' routing tables will be reduced, compared to their routing tables before the summarization?

ARouter R1

BRouter R2

CRouters R1 and R2

DRouters R2 and R4

Answer : B

Router R1 is the one that performs the summarization of the two subnets (20.20.1.0/24 and 20.20.2.0/24) into the summarized route 20.20.0.0/16. However, R1 itself will not see any change in its routing table because it is directly connected to both subnets and already knows about them.

Router R2, which is in Area 49.0002, will benefit from this summarization because it previously had separate routes for both 20.20.1.0/24 and 20.20.2.0/24. After the summarization, R2 will only need to maintain a single route to 20.20.0.0/16, reducing the size of its routing table.

Router R4 does not directly benefit from the summarization because it is only connected to the Level 1 network and has no need for the summarized routes from R1. Thus, the summarization does not affect R4's routing table.

Question 7

Which component of the Nokia 7750 SR is in charge of performing the longest prefix match lookup on packets that arrive on the physical interfaces?

AControl Processing Module (CMP)

BMedia Dependent Adapter (MDA)

CSwitch Fabric (SF)

DInput/Output Module (IOM)

Answer : D

The Input/Output Module (IOM) is responsible for performing the longest prefix match (LPM) lookup on packets that arrive at the physical interfaces. The IOM performs this function by examining the destination IP address of incoming packets and using the routing table to determine the best match.

Nokia IS-IS Routing Protocol 4A0-112 Exam Questions