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Re: BGP terminology question

  • From: Tony Li
  • Date: Sun Nov 06 14:34:43 2005 


I understand BGP flapping to be announcements followed by
withdraws over a short period. I am seeing a peer with a large
number of announcements and the normal number of withdraws. Is
there a term to describe what I am seeing? I'd like to understand
what is happening, but I've been looking for more info and can't
seem to find anything. I suspect I am just not using the right
words to search.



If there isn't a term, why would a peer announce thousands of time
an hour with very few withdraws?



There is a term, it's called "broken".



A peer should never announce a route it has already announced
unless that route is withdrawn. (If the session goes down or is
reset, that counts as a withdrawal.)





There's another term for that behavior. It's called "compliant".



There are a number of good implementation reasons why it is
reasonable for an implementation to announce a route that it has
already announced (e.g., peer groups). Admittedly announcing
thousands of times an hour does NOT seem reasonable, but 'never' is
not a requirement of the BGP spec either.



Tony