Nokia 4A0-112 Exam Questions Instant Access

Question 1

Which of the following is NOT a required configuration step to successfully run IS-IS on a router?

AThe router needs to be associated with an IS-IS area ID.

BLayer-3 interfaces that will participate in IS-IS need to be identified.

CA reference bandwidth needs to be configured to calculate link costs.

DThe IS-IS context needs to be enabled.

Answer : C

While configuring a reference bandwidth (which is used to calculate link costs) can be useful, it is not strictly required for IS-IS to run. IS-IS uses default bandwidth values to calculate costs, and it can function without explicitly configuring a reference bandwidth.

Question 2

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 3

Which of the following is NOT a function of the control plane a router?

ATo exchange signaling messages with other routers.

BTo determine the best way to forward packets.

CTo establish routing paths to deliver packets from source to destination and to reestablish them in case of failure.

DTo utilize the forwarding tables to forward data packets towards their destination.

Answer : D

The data plane (or forwarding plane) is responsible for actually forwarding the data packets. It uses the information stored in the forwarding table to determine how to move packets from one interface to another toward their destination.

Question 4

An IS-IS router receives a CSNP that references an older LSP than the one in its local database. What action is taken?

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

BThe router sends a CSNP to its neighbor describing the newer LSPs in its database.

CThe router updates its database with the new sequence number and floods a copy of the LSP to its other neighbors.

DThe router sends a PSNP to its neighbor to request a copy of the LSP.

Answer : A

When a router receives a CSNP (Complete Sequence Number PDU) that references an older LSP (Link-State PDU) than the one in its local database, it indicates that the neighbor is missing newer information.

In response, the router sends back a PSNP (Partial Sequence Number PDU) to the neighbor, which includes a copy of the LSPs it has in its local database that the neighbor may not yet have. This helps to synchronize the link-state information between routers.

Question 5

Refer to the exhibit.

All routers in the diagram are running an interior gateway protocol (IGP) and have been configured with an ECMP value of 4. Router R5 advertises the prefix 192.168.3.0/24 using the IGP. Assuming all links have the same cost, how many entries for prefix 192.168.3.0/24 will be in router R3's routing table?

Answer : D

In this scenario, the routers are configured with an Equal-Cost Multi-Path (ECMP) value of 4, meaning they can utilize up to 4 equal-cost paths to reach a destination. Since Router R5 is advertising the 192.168.3.0/24 prefix and all links have the same cost, router R3 will receive multiple routes to reach this destination.

Given that all the routers (R1, R2, R3, R4, and R5) are connected in a way that can support multiple equal-cost paths, and assuming ECMP is set to 4, the routing table on Router R3 will have up to 4 entries for the prefix 192.168.3.0/24.

Thus, Router R3's routing table will contain 4 entries for the prefix 192.168.3.0/24.

Question 6

When using IS-IS in native mode for routing in a dual-stack IPv4/IPv6 environment, which of the following statements is FALSE?

AAll links are assumed to be IPv4- and IPv6-capable.

BThe same topology information is used to calculate the shortest path tree for both IPv4 and IPv6.

CIn a multi-area environment, the SPF algorithm needs to be run four times on each L1/L2 router.

DIt may lead to traffic black-holing if not properly designed.

Answer : C

In a dual-stack IPv4/IPv6 IS-IS environment, the SPF (Shortest Path First) algorithm is only run once per router for each protocol (IPv4 or IPv6). The topology is shared, but the SPF calculations for IPv4 and IPv6 are separate. This means that the SPF algorithm will run twice (once for IPv4 and once for IPv6) for each L1/L2 router, not four times.

Question 7

Consider the exhibit.

All routers are running IS-IS with IPv6 support enabled. Based on the topology shown, and the route tables of routers R3 and R4, which of the following statements is TRUE?

AThere is no route leaking configured on router R1 or router R2.

BRoute leaking is configured on router R1 but not on router R2.

CRoute leaking is configured on router R2 but not on router R1.

DRoute leaking is configured on both routers R1 and R2.

Answer : D

Based on the IPv6 route table output for R3 and R4, we can see that the routers have remote routes listed as 'Remote ISIS', indicating that the route is being advertised from a different area (area 49.01 or 49.02). This is a sign of route leaking, where routes from one area are being shared across areas.

The routes from R3 (level-1 router) are being advertised to R4 (level-1 router), and vice versa, with ISIS as the protocol. This implies that there is route leaking configured to allow information to pass between areas.

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