From: Paul Crist (pcrist@xxxxxxxxxxx)
Date: Sat Jun 02 2001 - 08:15:00 GMT-3
Darren,
>From Global Knowledge's ABGP training manual to match only /16 prefixes.
access-list 101 permit ip 0.0.0.0 255.255.255.255 255.255.0.0 0.0.0.0
Which ends up looking like this in you config:
access-list 101 permit ip any host 255.255.0.0
So you question with a /19 I would think would look like this:
access-list 101 permit ip any host 255.255.224.0
Anyone disagree?
Paul Crist
----- Original Message -----
From: "Darren Ward" <dward@pla.net.au>
To: <ccielab@groupstudy.com>
Sent: Saturday, June 02, 2001 6:16 AM
Subject: BGP: Match prefixes gt using access-list?
> Hi All,
>
> I've ben asked a damn good question by a co-worker and I must admit I'm
> not exactly sure how to solve it.
>
> Q: Filter BGP advertisements to a neighbour so that only routes that are
> /19 or better are advertised WITHOUT using a prefix-list.
>
> A:
>
> I know it will be a BGP extended IP access-list using the network/mask
> pair but can't figure out the mask section properly.
>
> access-list 100 permit ip 0.0.0.0 255.255.224.0 255.255.224.0
> 225.255.224.0
>
> Now, I _think_ this means match ANY network where the last 13 bits are
> all zero AND the last 13 bits of the netmask are all zeros but allow
> more zeros the base 13 bits (greater than /19)
>
> Is this correct?
>
> Darren Ward
> (Sydney June 27-28)
> **Please read:http://www.groupstudy.com/list/posting.html
**Please read:http://www.groupstudy.com/list/posting.html
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