[c-nsp] BGP Filter - Best Practice

Nick Hilliard nick at foobar.org
Tue Apr 16 14:12:39 EDT 2013

On 15/04/2013 21:44, Ahmed Hilmy wrote:
> I am using Prefix-list and as-path for BGP filter.
> But if i  apply Prefix-list as inbound filter at PE, then from PE to RR (
> Route Reflector ) i apply as-path filter, i think it is more scalable than
> modify Prefix-list continuously ? or use community ?
> If my question not clear please ask me.

it depends.

Prefix lists are very fast because they are implemented as a trie, and it
is very fast to look up an entry in a trie.

Community lists can be fast (standard, i.e. integer comparison) or slow
(extended, i.e. regular expression).

as-path lists are slow because they use regular expressions.

If you need to filter BGP updates, it is usually fastest to use prefix
lists or standard community lists.  It makes little difference whether you
use extended communities or as-path lists - both are slow.


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