From: afiddler (afiddler@xxxxxxxxx)
Date: Sun Oct 21 2001 - 12:42:57 GMT-3
I think Halabi does a really good job of explaining BGP route filtering on
pages 308-316 (new edition).
----- Original Message -----
From: "Rick Burts" <burts@mentortech.com>
To: "Brian Hescock" <bhescock@cisco.com>
Cc: "Rajeev Siddappa" <raj_lab@yahoo.com>; <ccielab@groupstudy.com>
Sent: Sunday, October 21, 2001 5:42 AM
Subject: Re: Wiered - Access list.
> Actually it is not a mistake. This is an application of extended access
> list used in BGP processing. In this context you interpret the 4
> parameters as: network (address), mask on network (how many bits of the
> address need to match), subnet mask, mask on subnet mask (how many bits
> of the subnet mask are significant) rather than the traditional source
> address, source mask, destination address, destination mask.
>
> You would interpret this as permit advertisement of 192.169.192.0
> 255.255.248.0 but it would not permit advertisement of 192.168.192.0
> 255.255.240.0.
>
> This implementation is a bit complex. It is the early version of the
> function supplied by prefix list for BGP and does the same thing: allow
> filtering on both address and mask length.
>
> Rick
>
> Rick Burts, CCSI CCIE 4615 burts@mentortech.com
> Mentor Technologies 240-568-6500 ext 6652
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>
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> On Sat, 20 Oct 2001, Brian Hescock wrote:
>
> > It doesn't seem like anyone is on-line tonight so I'll go ahead and
> > answer: it's a mistake. He put in a subnet mask instead of a host
> > address. It's not you... ;-)
> >
> > Brian
> >
> > Rajeev Siddappa wrote:
> >
> > >Hi friends,
> > >
> > >Can any one explain me how this access-list works.
> > >
> > >access-list 101 permit IP host 192.169.192.0 host
> > >255.255.248.0
> > >
> > >This is an example in Jeff-doyel vloume 2 page 189.
> > >
> > >Please I am breaking my head.
> > >
> > >Thank you,
> > >Rajeev.
> > >
> > >
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