300-510 · Question #211
Refer to the exhibit. IS-IS is the routing protocol on the network. After the team noticed excessive CPU usage on all routers, particularly routers R2 and R6, they configured route summarization on al
The correct answer is B. Configure R3 to perform summarization for Level 1 routers, and configure R6 to perform. In IS-IS, Level 1 (intra-area) routers only see routes leaked by their Level 1/Level 2 (L1/L2) border routers. When summarization is applied, it must be done at the L1/L2 boundary routers so that only summary routes are leaked into the L1 area. R3 acts as the L1/L2 border router
Question
Refer to the exhibit. IS-IS is the routing protocol on the network. After the team noticed excessive CPU usage on all routers, particularly routers R2 and R6, they configured route summarization on all routers. However, a network engineer noticed that summary routes and more specific routes are present in the routing table on R1. Which action must the team take so that R1 receives only the summary routes?
Exhibit
Options
- AConfigure R2 and R4 to perform summarization for Level 1 routers.
- BConfigure R3 to perform summarization for Level 1 routers, and configure R6 to perform
- CConfigure R3 and R5 to perform summarization for Level 1 and Level 2 routers.
- DConfigure R6 only to perform summarization for all routers.
How the community answered
(24 responses)- A4% (1)
- B75% (18)
- C13% (3)
- D8% (2)
Explanation
In IS-IS, Level 1 (intra-area) routers only see routes leaked by their Level 1/Level 2 (L1/L2) border routers. When summarization is applied, it must be done at the L1/L2 boundary routers so that only summary routes are leaked into the L1 area. R3 acts as the L1/L2 border router responsible for summarizing routes for its L1 area, and R6 acts as the L1/L2 border router for another segment. Configuring both R3 and R6 to summarize Level 1 routes ensures that R1 (an L1 router) receives only the aggregate summary routes and not the more-specific prefixes from the Level 2 backbone.
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