Refer to the exhibit. An engineering team implemented IS-IS on the network, with several different areas. Recently, router R6 in area 3 has been experiencing excessive CPU usage. To reduce the load, a

Question

Exhibit

Options

• AConfigure routers R3 and R5 to send summary routes to R6.
• BConfigure the Level 2 router R6 to manage summarization for the network.
• CConfigure router R1 to send only the default route to R2 and R4.
• DConfigure all routers as Level 1/2 routers so that route summarization functions throughout the

• A
  78% (46)
• B
  5% (3)
• C
  14% (8)
• D
  3% (2)

Explanation

In IS-IS, route summarization is performed at the boundary between Level 1 and Level 2 routing domains. Level 1/2 routers that sit on the boundary between areas are responsible for redistributing (leaking) Level 1 routes into Level 2 and vice versa. If R6 is in area 3 and is a Level 1 router, it receives its external routing information from the nearest Level 1/2 boundary routers - in this topology, R3 and R5. Even if R2 is correctly summarizing routes, R3 and R5 are likely still leaking full Level 2 routes into area 3. The fix is to configure route summarization on R3 and R5 so they advertise only summary routes into area 3 toward R6. Option B is incorrect because R6 is a Level 1 router and cannot perform inter-area summarization. Options C and D do not address the specific boundary where summarization must occur.

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