On Monday 31 July 2006 12:24, Hari Kurup wrote: > Ok but I get zero prefixes from 28941.
My suggestion, in the interest of fast growth and scalability of the exchange point, rather than explicitly defining which prefixes members announce at the exchange point, why don't we instead deny RFC 1918, test networks, multicast networks (unless you need them), bogon, your own prefixes, e.t.c. and accept everything else (with a maximum prefix length being optional). This way, networks can update their peering information without having to bother everyone else with making changes to their filtering (which could potentially cause typographical errors and route propagation delays). I normally use something like this (this is for a full BGP feed peering session with one of my upstreams, but you can apply the same concept to your exchange point peering routers, as they sit between your AS and other AS's): ip prefix-list comone-in seq 20 deny 10.0.0.0/8 le 32 ip prefix-list comone-in seq 30 deny 127.0.0.0/8 le 32 ip prefix-list comone-in seq 40 deny 169.254.0.0/16 le 32 ip prefix-list comone-in seq 50 deny 172.16.0.0/12 le 32 ip prefix-list comone-in seq 60 deny 192.0.2.0/24 le 32 ip prefix-list comone-in seq 70 deny 192.42.172.0/24 le 32 ip prefix-list comone-in seq 80 deny 192.168.0.0/16 le 32 ip prefix-list comone-in seq 90 deny 198.18.0.0/15 le 32 ip prefix-list comone-in seq 100 deny 224.0.0.0/4 le 32 ip prefix-list comone-in seq 110 deny 240.0.0.0/4 le 32 ip prefix-list comone-in seq 120 deny 216.104.192.0/21 le 32 ip prefix-list comone-in seq 121 deny 196.43.96.0/19 le 32 ip prefix-list comone-in seq 130 deny 209.88.92.0/24 le 32 ip prefix-list comone-in seq 999 permit 0.0.0.0/0 le 24 You will note that sequence lines 120, 121 and 130 are my own prefixes that I originate to the Internet. I do not expect to receive them in any BGP updates from my upstreams (loop/spoofing prevention). For some ISP's/members with smaller assignments, e.g., /25 or longer, you may need to make adjustments to sequence line 999. It wouldn't be a good idea to use this measure (filter at /24) at the exchange point, where connectivity from all ISP's, large and small, is vital. Cheers, Mark.
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