Nokia 4A0-112 Exam Questions

The routing table manager (RTM) is responsible for selecting the best route when multiple routing protocols provide a route for the same destination prefix. It makes the decision on which route to add to the routing table based on the administrative distance, metric, and other criteria.

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.

From the route tables of R3 and R4, we can see that remote routes are present, with R3 and R4 both having routes referencing routers in different areas (Area 49.01 and 49.02). These remote routes are characteristic of route leaking, which is the process of sharing routes between different IS-IS areas.

R3 has routes for R1, R2, and R4, which are in Area 49.01, suggesting that R1 and R2 have advertised their routes to R3, possibly due to route leaking.

R4 has similar routes for R2 and R3, indicating that R2 might have advertised its routes to R4.

This sharing of routes between areas is indicative of route leaking being configured on both R1 and R2, allowing these routes to be shared across the areas.

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 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.