Re: commonly accepted prefix length filters?

["John M . Brown" <jmbrown () ihighway net>]

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