BGP community attribute is an optional transitional attribute, which is a routing label and is used to simplify the execution of routing policies. It is divided into custom community attributes and…

Question

Options

• ANo_Export
• BInternet
• CNo_Advertise
• DNo_Export Subconfied

• A
  100% (32)

Explanation

All four options are well-known public BGP community attributes standardized in RFC 1997, which is why the answer is A, B, C, D. Internet (B) is the default community allowing routes to be advertised to all peers. No_Export (A) prevents routes from being advertised outside the local AS or confederation boundary. No_Advertise (C) prevents routes from being advertised to any BGP peer, including internal ones. No_Export_Subconfed (D) restricts advertisement within a BGP confederation, keeping routes inside a single member AS - note the question spells it "Subconfied," which is a typo for "Subconfed."

Since all four are correct, there are no distractors to eliminate here - the trap is assuming some options must be "custom" attributes when in fact all four are part of the RFC 1997 standard set.

Memory tip: Think of the public communities as a spectrum of advertisement restriction - Internet (share freely) → No_Export_Subconfed (stay in sub-AS) → No_Export (stay in AS) → No_Advertise (tell no one). RFC 1997 defines exactly these four, so if you see any of them on an exam, they are always "public/well-known."

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