From: Geert Nijs (Geert.Nijs@simac.be)
Date: Wed Aug 27 2008 - 13:39:55 ART
Hi group,
I was wondering if it is technically possible to do the following:
I have a BGP connection to a router. I receive 2000 prefixes on this connection, all pointing to the same next hop.
Some prefixes are specific, some are more general and they do overlap.
I would like to reduce (summarize or surpress) these routes into the least amount of prefixes.
I want to tackle the following situation:
Suppose i receive the following network: 139.136.0.0/17
In addition to this network, i also receive the following smaller prefixes:
sh ip route 139.136.0.0 255.255.128.0 longer-prefixes
B 139.136.3.0/24 [150/0] via 193.74.134.5, 2d04h
B 139.136.0.0/17 [150/0] via 193.74.134.5, 2d04h
B 139.136.7.0/24 [150/0] via 193.74.134.5, 2d04h
B 139.136.4.0/24 [150/0] via 193.74.134.5, 2d04h
B 139.136.10.0/23 [150/0] via 193.74.134.5, 2d04h
B 139.136.9.0/24 [150/0] via 193.74.134.5, 2d04h
B 139.136.12.0/23 [150/0] via 193.74.134.5, 2d04h
B 139.136.33.0/26 [150/0] via 193.74.134.5, 00:53:47
B 139.136.47.0/24 [150/0] via 193.74.134.5, 2d04h
B 139.136.50.0/24 [150/0] via 193.74.134.5, 2d04h
B 139.136.49.0/24 [150/0] via 193.74.134.5, 2d04h
B 139.136.53.0/24 [150/0] via 193.74.134.5, 2d04h
B 139.136.67.0/24 [150/0] via 193.74.134.5, 2d04h
B 139.136.66.0/24 [150/0] via 193.74.134.5, 2d04h
B 139.136.65.0/24 [150/0] via 193.74.134.5, 2d04h
B 139.136.72.0/22 [150/0] via 193.74.134.5, 2d04h
B 139.136.91.0/24 [150/0] via 193.74.134.5, 2d04h
B 139.136.103.0/27 [150/0] via 193.74.134.5, 2d04h
B 139.136.102.0/23 [150/0] via 193.74.134.5, 2d04h
B 139.136.51.64/26 [150/0] via 193.74.134.5, 2d04h
B 139.136.123.0/24 [150/0] via 193.74.134.5, 2d04h
B 139.136.126.0/24 [150/0] via 193.74.134.5, 2d04h
B 139.136.125.0/24 [150/0] via 193.74.134.5, 2d04h
B 139.136.124.0/24 [150/0] via 193.74.134.5, 2d04h
B 139.136.5.128/25 [150/0] via 193.74.134.5, 2d04h
B 139.136.59.192/27 [150/0] via 193.74.134.5, 2d04h
I want to surpress these prefixes, because they are already covered by the 139.136.0.0/17 prefixes.
But i -only- want to surpress them as long as the "summary" 139.136.0.0/17 is received.
In the case i stop receiving the summary 139.136.0.0/17, the router should start announcing the more specific prefixes.
Possible ?
Geert
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