The Error Code of the BGP Notification message is 2, it means that the OPEN message is wrong. Which of the following error subcodes are contained in it? (Multiple choice)

Question

Options

• A3- Wrong BCP Router ID
• B2- Unacceptable AS number
• C4- Incorrect property list
• D2- Incorrect peer AS number

• A
  71% (22)
• C
  29% (9)

Explanation

BGP Error Code 2 signals an OPEN Message Error, which occurs during the initial BGP handshake when a peer's OPEN message contains invalid parameters. Options A, B, and D are correct because they accurately reference valid subcodes defined in RFC 4271: Subcode 3 identifies a Bad BGP Identifier (Wrong Router ID), and Subcode 2 identifies a Bad Peer AS - both B and D correctly describe Subcode 2 using slightly different but equivalent terminology ("Unacceptable AS number" vs. "Incorrect peer AS number").

Option C is the distractor: while Subcode 4 does exist, it is defined as "Unsupported Optional Parameter" - not "Incorrect property list." The description in C is fabricated and doesn't match the RFC standard, making it incorrect regardless of the subcode number.

Memory tip: For BGP OPEN errors, remember the acronym "VIP-UH" - Version (1), Identity/AS (2), Property-bad (3 = Router ID), Unsupported-parameter (4), Hold-time (6). When you see "property list" on an exam, that's a red flag - the real subcode 4 is about optional parameters, not a generic "property list."

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