From: Geert Nijs (geert.nijs@simac.be)
Date: Fri Apr 20 2007 - 11:13:14 ART
Hi group,
I am having a bit of a problem with the following challenge:
Suppose you have a router with a BGP connection. Over this BGP connection the following prefixes are received:
192.168.2.0 / 24
192.168.3.0 / 24
192.168.4.0 / 24
For some specific ranges, i do not want the very specific prefixes, but i only want a summary to be installed into the routing table.
For example: i would like to summarize the above prefixes into 192.168.0.0 / 16 and i only want 192.168.0.0 / 16 in my routing table.
Generating the summary is not difficult:
router bgp 6500
aggregate-address 192.168.0.0 255.255.0.0 summary-only
This generates the summary and supresses (in BGP !!) the specific prefixes (for outbound BGP advertisements)
sh ip bgp
*> 192.168.0.0/16
s> 192.168.2.0
s> 192.168.3.0
s> 192.168.4.0
However, in the routing table, all prefixes are still installed:
192.168.0.0 / 16
192.168.2.0 / 24
192.168.3.0 / 24
192.168.4.0 / 24
I could filter the 192.168.x.0 / 24 prefixes inbound on the BGP session, so that they do not get to the BGP table,
but this would prevent the summary from being generated, because there is not at least one specific route. Sort of a chicken and egg problem:
i don't want the specific prefixes in my routing table, but i can't filter them off otherwise the summary isn't generated any more.......
Is there a way to prevent the specific routes from being installed into the routing table, however, still generating the summary.....
regards,
Geert
This archive was generated by hypermail 2.1.4 : Tue May 01 2007 - 08:28:36 ART