Which of the following descriptions about the Originator_ID attribute in BGP is correct? (Multiple choice) A. Originator_ID is a recognized arbitrary attribute. B. If there are multiple RRs in an…

Question

Options

• AOriginator_ID is a recognized arbitrary attribute.
• BIf there are multiple RRs in an AS, the Originator_ID attribute is created by the first RR
• CWhen a route is reflected by RR for the first time, RR adds the Originator_ID attribute to this route to identify the originating router of this route.
• DIf the Originator_ID attribute already exists, RRs will compare the received Originator_ID with the local RouterID. If the two IDs are the same, BGPSpeaker will ignore this route and do not process it.

• A
  13% (5)
• B
  82% (31)
• D
  5% (2)

Explanation

B and C are correct because Originator_ID is added by the first Route Reflector (RR) that reflects a route - it is set to the Router-ID of the route's originating client. If additional RRs subsequently reflect that same route, they leave the existing Originator_ID unchanged; only the first RR creates it. This makes both B and C accurate descriptions of the attribute's lifecycle.

A is wrong because Originator_ID is not an "arbitrary" attribute - it is a well-defined optional, non-transitive BGP path attribute (type code 9, per RFC 4456). "Arbitrary" implies no standard definition, which is incorrect.

D is wrong in a subtle but important way: the loop-prevention check (comparing received Originator_ID against the local Router-ID and dropping the route on a match) is performed by any BGP speaker - not exclusively by RRs. D incorrectly restricts this behavior to RRs only.

Memory tip: Think of Originator_ID as a "birth certificate" - the first RR stamps it once with the originator's ID, no one overwrites it, and any router that sees its own ID on that certificate throws the route away.

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