Click the exhibit. Which of the following is a valid confederation configuration for Router R2?

Question

Options

• AR2>config>router# info autonomous-system 65540 confederation 65540 members 65541 65542
• BR2>config>router# info autonomous-system 65542 confederation 65540 members 65541
• CR2>config>router# info autonomous-system 65542 confederation 65540 members 65541 65542
• DR2>config>router# info autonomous-system 65540 confederation 65542 members 65541

• A
  14% (6)
• B
  10% (4)
• C
  74% (31)
• D
  2% (1)

Explanation

Option C is correct because Router R2 belongs to sub-AS 65542, so its autonomous-system must be 65542 - not the confederation identifier 65540. The confederation 65540 declares the external-facing AS number that peers outside the confederation see, and members 65541 65542 must list all sub-ASes in the confederation (including R2's own) so the router can correctly apply confederation iBGP rules and identify confederation-internal paths.

Why the distractors fail:

• A sets autonomous-system 65540, which is the confederation identifier itself - no router should claim the confederation ID as its own sub-AS.
• B gets the autonomous-system right (65542) but omits 65542 from the members list; all sub-ASes, including your own, must be declared so the router recognizes confederation-internal routes.
• D doubles down on two errors: wrong autonomous-system (65540 again) and swaps the confederation ID with a member AS number, inverting the whole structure.

Memory tip: Use the phrase "I am a member, not the club" - your autonomous-system is always your member sub-AS (the small number belonging to you), while confederation holds the club's public ID (the number the outside world sees), followed by all member sub-ASes including your own.

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