From: Rick Burts (burts@xxxxxxxxxxxxxx)
Date: Sun Oct 21 2001 - 07:42:16 GMT-3
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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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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