What will happen if an update is received with an unrecognized optional non-transitive attribute?

Question

Options

• AThe router will accept the update and send a notification.
• BThe router will not accept the update and send a notification.
• CThe router will accept the update and ignore the attribute.
• DThe router will accept the update and propagate the attribute.

• A
  6% (2)
• B
  3% (1)
• C
  91% (31)

Explanation

Option C is correct because BGP defines specific handling rules for attribute types. An optional non-transitive attribute is one that routers are not required to recognize, and if unrecognized, the router should silently discard the attribute while still accepting the UPDATE message and installing the route normally - no error or notification is generated.

Why the distractors are wrong:

• A & B are wrong because no notification is sent - notifications in BGP signal errors (like malformed messages), not routine attribute handling. The router simply drops the unknown attribute quietly.
• B is additionally wrong because the router does accept the update; rejecting it would be incorrect behavior per RFC 4271.
• D describes the behavior of an optional transitive attribute - if unrecognized but transitive, the router accepts and forwards it (marked with the Partial bit). Non-transitive means "don't pass it on."

Memory tip: Think of the word non-transitive literally - it doesn't transit (pass through). If a router doesn't recognize it, the attribute stays local and gets dropped. Pair that with "optional" = no error required, and you get: accept the route, ignore the attribute, tell nobody.

No community discussion yet for this question.