iBGP Multipath and Route Reflector

From: gladston@br.ibm.com
Date: Tue Jun 14 2005 - 18:45:43 GMT-3

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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