4A0-112 Nokia IS-IS Routing Protocol Questions and Answers

Thedata 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.

The static route configured on router R1 uses an indirect next-hop, which is10.10.10.3 (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 route10.4.100.0/24is reachable throughR3, but there is no reciprocal route inR3's routing table that allows the response to flow back towardsR1. This results in a failure to return the echo response to R1, causing the ping to fail.

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.

In IPv6, consecutive sections of zeros can be abbreviated with a double colon (::) once in an address. Also, leading zeros in each hextet (group of four hexadecimal digits) can be removed.

The original address is2001:0da8:0000:0000:0024:0000:4ab9:0300.

Removing leading zeros and applying the abbreviation:

0da8becomesda8.

0000becomes0(and multiple consecutive 0000 sections can be represented by ::).

The final result becomes2001:da8::24:0:4ab9:300, which matches option A when properly formatted.

While configuring areference 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.

In the configuration on router R1, the static route is defined with the next-hop IP address of139.120.121.1.

However, the next-hop IP address139.120.121.1does not belong to the same subnet as the directly connected interface on R1, which is172.31.1.1/30. 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).

Route redistributionis the process of sharing routing information between different routing protocols or routing domains. For example, a router might redistribute routes learned via OSPF into a BGP routing table or vice versa. This enables routers to exchange routing information even when they are using different routing protocols.

When a link-state update reaches its maximum age, it isremovedfrom the router’s link-state database, not flooded to its neighbors. This prevents outdated information from continuing to affect the routing decisions. The router does not flood the aged update; instead, it will typically request a new link-state advertisement from the original source router if the information is still needed.

IS-IS routers must have matching authentication settings to establish an adjacency. If one router is configured with authentication and the other is not, the routers will not be able to establish an adjacency because their authentication parameters do not match.