[46858] in North American Network Operators' Group
RE: genuity - any good?
daemon@ATHENA.MIT.EDU (David Luyer)
Fri Apr 12 22:44:49 2002
From: "David Luyer" <david@luyer.net>
To: "'Martin, Christian'" <cmartin@gnilink.net>, <neil@DOMINO.ORG>,
<garlic@garlic.com>
Cc: <matthew@velvet.org>, <nanog@merit.edu>
Date: Sat, 13 Apr 2002 12:44:02 +1000
Message-ID: <008101c1e295$12b34eb0$46943ecb@pacific.net.au>
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Errors-To: owner-nanog-outgoing@merit.edu
> I think the argument is not about route filtering - it is the
> implementation method.
>
> Genuity uses ip extended access-lists.
>
> Everyone else uses prefix-lists.
>
> To a purist, the former is more granular, but performs poorly
> because it is a linked list implementation. The later, while
> less granular, performs faster by using a trie.
IOS 12.0S (and derivatives) are popular with ISPs (at least those
who use Ciscos), and support 'access-list compiled', making
access-lists likely to be around the same speed as prefix lists;
they just take up RAM (one access list I use takes 10Mb of RAM
once compiled).
extended access lists still permit flexibility, ie, the /16
permitted only:
access-list 111 permit ip host 192.168.0.0 host 255.255.0.0
becomes to permit all /16 thru /24 under that:
access-list 111 permit ip 192.168.0.0 0.0.255.0 255.255.0.0 0.0.255.0
(might look less clear than a prefix list when you start wanting to
let them permit say /19 thru /22, but then, router configs come from
automated systems now, right? :-))
David.
--
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