Refer to the exhibit. Routers R2, R3, R4 and R5 all reside in the same area, with R1 in a different area R3 is overutilized and the engineer wants to reduce its CPU load. The engineer configured…

The correct answer is A. Configure R3 in a new area. IS-IS route summarization only occurs at the boundary between Level 1 and Level 2 - i.e., at an L1/L2 ABR when routes are promoted from L1 to L2 or vice versa. All of R2, R3, R4, and R5 are in the same IS-IS area. Since they are all at the same level, there is no L1/L2 boundary…

Unicast Routing

Question

Refer to the exhibit. Routers R2, R3, R4 and R5 all reside in the same area, with R1 in a different area R3 is overutilized and the engineer wants to reduce its CPU load. The engineer configured router R4 to summarize routes that it receives from R5, but R3 is still receiving all of the R5 routes. Which action resolves the issue?

Exhibit

Options

AConfigure R3 in a new area,
BConfigure R2 as a Level 1 router
CConfigure the summary routes on R5.
DConfigure R4 as a Level I-Level 2 router

How the community answered

(37 responses)

A
65% (24)
B
19% (7)
C
11% (4)
D
5% (2)

Explanation

IS-IS route summarization only occurs at the boundary between Level 1 and Level 2 - i.e., at an L1/L2 ABR when routes are promoted from L1 to L2 or vice versa. All of R2, R3, R4, and R5 are in the same IS-IS area. Since they are all at the same level, there is no L1/L2 boundary between them, and IS-IS does not support summarization between routers within the same area. R4 cannot summarize R5's routes for R3 because there is no area boundary between them. By moving R3 into a new (separate) area, R4 becomes an L1/L2 ABR sitting between R3's area and the existing area. R4 can then summarize routes at this inter-area boundary, reducing the number of prefixes R3 receives and lowering its CPU load.

Topics

#OSPF Inter-Area Routing#OSPF Summarization#OSPF Area Design#Route Optimization

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