Click the exhibit. AS 65100 is advertising 192.168.1.0/27 into BGP. Which of the following AS Paths would the prefix 192.168.1.0/27 contain when viewed on router R7?

Question

Options

• A65206 65202 65100
• B(65206 65202)65100
• C(65204 65206 65202) 65100
• D(65200) 65100

• A
  5% (1)
• B
  75% (15)
• C
  15% (3)
• D
  5% (1)

Explanation

Option B is correct because this topology uses BGP Confederations, where sub-AS members (65206 and 65202) appear in parentheses as an AS_CONFED_SEQUENCE in the AS Path attribute - these sub-ASes are visible internally but are stripped before advertising to external peers, so R7 sees them in parentheses followed by the true originating AS 65100.

• A is wrong because it lists 65206 65202 65100 with no parentheses, which would be a standard eBGP path - confederations require parentheses around sub-AS members to distinguish them from regular AS hops.
• C is wrong because it includes AS 65204 in the confederation segment, which the exhibit shows is not in the forwarding path between 65206, 65202, and R7.
• D is wrong because (65200) suggests a single confederation sub-AS traversal, collapsing the actual two-hop confederation path and using the wrong AS numbers entirely.

Memory tip: Think of parentheses as a "confederation carpool lane" - multiple sub-ASes share the ride inside ( ), while the external AS rides alone outside. If you see parentheses in a BGP path, you're looking at confederation internals.

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