[36963] in North American Network Operators' Group
Re: commonly accepted prefix length filters?
daemon@ATHENA.MIT.EDU (John M . Brown)
Fri Apr 27 11:27:38 2001
Date: Fri, 27 Apr 2001 08:19:56 -0700
From: "John M . Brown" <jmbrown@ihighway.net>
To: "Stephen J. Wilcox" <steve@opaltelecom.co.uk>
Cc: Jim Mercer <jim@reptiles.org>, nanog@merit.edu
Message-ID: <20010427081956.C57921@gremlin.chagres.net>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <Pine.LNX.4.21.0104271602370.19937-100000@staff.opaltelecom.net>; from steve@opaltelecom.co.uk on Fri, Apr 27, 2001 at 04:06:31PM +0100
Errors-To: owner-nanog-outgoing@merit.edu
Some people use filters such as the example provided
ip prefix-list bad-nets-in description input prefix-list for BGP sessions
ip prefix-list bad-nets-in seq 1 deny 0.0.0.0/1 ge 21
ip prefix-list bad-nets-in seq 2 deny 0.0.0.0/8 le 32
ip prefix-list bad-nets-in seq 3 deny 10.0.0.0/8 le 32
ip prefix-list bad-nets-in seq 4 deny 127.0.0.0/8 le 32
ip prefix-list bad-nets-in seq 5 deny 128.0.0.0/2 ge 21
ip prefix-list bad-nets-in seq 6 deny 128.0.0.0/16 le 32
ip prefix-list bad-nets-in seq 7 deny 169.254.0.0/16 le 32
ip prefix-list bad-nets-in seq 8 deny 172.16.0.0/12 le 32
ip prefix-list bad-nets-in seq 9 deny 191.255.0.0/16 le 32
ip prefix-list bad-nets-in seq 10 deny 192.0.0.0/3 ge 25
ip prefix-list bad-nets-in seq 11 deny 192.0.0.0/24 le 32
ip prefix-list bad-nets-in seq 12 deny 192.0.2.0/24 le 32
ip prefix-list bad-nets-in seq 13 deny 192.168.0.0/16 le 32
ip prefix-list bad-nets-in seq 14 deny 198.32.175.0/24 le 32
ip prefix-list bad-nets-in seq 15 deny 198.32.176.0/24 le 32
ip prefix-list bad-nets-in seq 16 deny 198.32.177.0/24 le 32
ip prefix-list bad-nets-in seq 17 deny 223.255.255.0/24 le 32
ip prefix-list bad-nets-in seq 18 permit 0.0.0.0/0 ge 1
On Fri, Apr 27, 2001 at 04:06:31PM +0100, Stephen J. Wilcox wrote:
>
> I'm seeing 103000 routes..
>
> I imagine the limit on what you discard has to be that of the smallest
> block of addresses that the registries will allocate, as if you filter
> anything smaller you will start to lose genuine networks. Not sure what
> that limit is, /24 ?
>
> Steve
>
> On Fri, 27 Apr 2001, Jim Mercer wrote:
>
> >
> >
> > our bgp tables are starting (?) to get out of hand.
> >
> > we are thinking maybe we should start nuking some routes in order to reduce
> > the size of the tables.
> >
> > is there a list of commonly accepted aggregating prefix filters?
> >
> >
> >
>
> --
> Stephen J. Wilcox
> IP Services Manager, Opal Telecom
> http://www.opaltelecom.co.uk/
> Tel: 0161 222 2000
> Fax: 0161 222 2008
>
>
