Comprehensive and Detailed In-Depth Explanation:To determine which statement is false, we need to analyze the IS-IS topology, the role of multi-topology, the IPv6 summary configuration, and the level-1-2 behavior of IS-IS routers. Let's break it down step by step:
* Understanding the IS-IS Topology and Levels:
* IS-IS supports multiple levels: Level-1 (L1) for intra-area routing, Level-2 (L2) for inter-area routing, and Level-1-2 (L1-2) routers that can operate in both levels and connect L1 and L2 areas.
* In the figure, R1 and R2 are configured as Level-1-2 routers, R3 is a Level-1-2 router, R4 is a Level-1 router, and R5 is a Level-1 router. The area borders are indicated by the system IDs (49.0001 for R4's area and 49.0002 for R3 and R5's area).
* R4's Loopback0 has the IPv6 address 2000::/128, which is a host route (a /128 prefix, representing a single address).
* Multi-Topology IS-IS for IPv6:
* Multi-topology IS-IS allows separate topologies for IPv4 and IPv6, ensuring that IPv6 routes are handled independently. Since multi-topology is enabled on all routers, IPv6 routes (like 2000::
/128 on R4) are advertised and processed within the IPv6 topology.
* This means that IPv6 routes, including the Loopback0 address of R4 (2000::/128), can be advertised across the IS-IS domain, subject to the level and summary configurations.
* IPv6 Summary Configuration (2000::/64 level-1-2):
* The command ipv6 summary 2000::/64 level-1-2 is configured in the IS-IS processes of R1 and R2. This command instructs R1 and R2 (as Level-1-2 routers) to summarize the IPv6 prefix
2000::/64 and advertise it to both Level-1 and Level-2 areas.
* Summarization means that instead of advertising the more specific route (e.g., 2000::/128 from R4), R1 and R2 advertise the less specific summary route 2000::/64. This summary route covers the 2000::/128 address of R4's Loopback0.
* Since R1 and R2 are Level-1-2 routers, they can advertise this summary to both their Level-1 neighbors (like R4 and R3) and Level-2 neighbors (across areas).
* Analyzing Each Statement:
* A. The routing table of R1 contains the route 2000::/64.
* True. R1 is a Level-1-2 router with the ipv6 summary 2000::/64 level-1-2 command configured. It advertises and installs the summary route 2000::/64 in its routing table, covering the more specific 2000::/128 from R4. Additionally, as a Level-1-2 router, R1 can learn and retain this route from its IS-IS neighbors.
* B. The routing table of R2 contains the route 2000::/64.
* True. Similar to R1, R2 is also a Level-1-2 router with the same summary command. It advertises and installs the 2000::/64 summary route in its routing table, covering R4's
2000::/128.
* C. The routing table of R3 contains the route 2000::/128.
* False. R3 is a Level-1-2 router in area 49.0002, but it receives routes from R2 (a Level-1-2 router in area 49.0001). Because R1 and R2 are configured with the ipv6 summary 2000::
/64 level-1-2 command, they advertise the summary route 2000::/64 to their neighbors, including R3. IS-IS prefers the most specific route, but the summary configuration ensures that the more specific 2000::/128 from R4 is not advertised beyond R1 and R2 unless explicitly allowed. Since R3 is in a different area and receives the summary 2000::/64 from R2, it does not have the more specific 2000::/128 route in its routing table. Therefore, this statement is false.
* D. The routing table of R2 contains the route 2000::/128.
* True. R2, as a Level-1-2 router, is directly connected to R4 (a Level-1 router) via the IS-IS topology. R4 advertises its Loopback0 address 2000::/128 to R2. Even though R2 is configured to summarize 2000::/64, it can still retain the more specific 2000::/128 route in its routing table because IS-IS allows routers to keep both summary and more specific routes, with the more specific route taking precedence for routing decisions.
* Conclusion:
* The false statement is C, as R3 does not contain the route 2000::/128 in its routing table. Instead, R3 receives the summary route 2000::/64 from R2 due to the summary configuration on R1 and R2.
References to HCIP-Datacom-Advanced Routing & Switching Technology Documents:
* HCIP-Datacom-Advanced Routing & Switching Technology V1.0, Section on IS-IS: Multi-Topology IS-IS for IPv6, Level-1 and Level-2 Operations, and Route Summarization.
* HCIP-Datacom-Advanced Routing & Switching Technology V1.0, Chapter on IPv6 Routing Protocols:
IS-IS Configuration and Behavior, Including Summary Address Commands and L1/L2 Interactions.