From: glcassels3 (glcassels3@nc.rr.com)
Date: Thu Jun 16 2005 - 22:07:38 GMT-3
Gladston,
I can not verify this because I can not see your entire configs and
topology, but I did a lab this week and found out that BGP multi-hope (can't
remember ibgp for ebgp) will use the IGP metric to reach the next hope
address in BGP. So even if all other things are equal in BGP unless the IGP
metric to the next hops are the same BGP will not load balance. You can see
this when you do the sh ip bgp {prefix} command. The IGP metric when the
IGP metric is different can be seen in (). If the IGP metric is the same
the () with the metric will not be there. Truthfully I find the sh ip bgp
{prefix} to be a much more useful command then just sh ip bgp.
Thanks Val!!
George
>On Tue, 14 Jun 2005 17:45:43 -0400 gladston@br.ibm.com wrote.
>Hi,
>
>It seems iBGP multipath does not work when using Route Reflector.
>(at least it was the result of the lab).
>
>It works fine without RR:
>
>R14#sb 2.2.2.0
>BGP routing table entry for 2.2.2.0/24, version 2
>Paths: (2 available, best #2, table Default-IP-Routing-Table)
>Multipath: iBGP
> Not advertised to any peer
> Local
> 142.20.28.8 from 142.20.28.8 (142.20.8.1)
> Origin IGP, metric 0, localpref 100, valid, internal, multipath
> Local
> 142.20.28.2 from 142.20.28.2 (142.20.2.1)
> Origin IGP, metric 0, localpref 100, valid, internal, multipath, best
>R14#
>R14#sir 2.2.2.0
>Routing entry for 2.2.2.0/24
> Known via "bgp 65202", distance 200, metric 0, type internal
> Last update from 142.20.28.2 00:00:58 ago
> Routing Descriptor Blocks:
> * 142.20.28.8, from 142.20.28.8, 00:00:58 ago
> Route metric is 0, traffic share count is 1
> AS Hops 0
> 142.20.28.2, from 142.20.28.2, 00:00:58 ago
> Route metric is 0, traffic share count is 1
> AS Hops 0
>
>
>Now, with RR (R1 is the RR):
>
>Rack2R1#sb 2.2.2.0
>BGP routing table entry for 2.2.2.0/24, version 2
>Paths: (2 available, best #2, table Default-IP-Routing-Table)
>Multipath: iBGP
> Advertised to non peer-group peers:
> 142.20.125.5
> Local, (Received from a RR-client)
> 142.20.125.5 from 142.20.125.5 (142.20.5.1)
> Origin IGP, metric 0, localpref 100, valid, confed-internal
> Local, (Received from a RR-client)
> 142.20.125.2 from 142.20.125.2 (142.20.2.1)
> Origin IGP, metric 0, localpref 100, weight 65000, valid,
confed-internal, best
>Rack2R1#
>
>Rack2R1#sir 2.2.2.0
>Routing entry for 2.2.2.0/24
> Known via "bgp 65202", distance 200, metric 0, type internal
> Last update from 142.20.125.2 00:33:03 ago
> Routing Descriptor Blocks:
> * 142.20.125.2, from 142.20.125.2, 00:33:03 ago
> Route metric is 0, traffic share count is 1
> AS Hops 0
>
>Rack2R1#
>
>Do you have other experience?
>
>(R1, R2 and R5 are on the same confederation, and is the same of R14, R2
and CAT2, so it seems confederation does not have influence on this result)
>
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