[c-nsp] interesting ASR 9k bgp multipath issue

[John van Oppen]

So, to be clear, here is an example of this working right on a 6500 with IOS   (multipath on the ibgp route that is the same IGP cost and not on the one that is not):

cr1-pdx#show ip bgp 64.187.160.0
BGP routing table entry for 64.187.160.0/20, version 562475581
Paths: (2 available, best #1, table Default-IP-Routing-Table)
Multipath: eBGP iBGP
Flag: 0x1000
  Advertised to update-groups:
     1          3          5          6          7          8
  54858
    208.76.153.78 (metric 516) from 208.76.153.116 (208.76.153.116)
      Origin IGP, metric 0, localpref 115, valid, internal, multipath, best
      Community: 11404:993 11404:4000 11404:4010
      Originator: 208.76.153.78, Cluster list: 208.76.153.116
  54858
    208.76.153.79 (metric 516) from 208.76.153.117 (208.76.153.117)
      Origin IGP, metric 0, localpref 115, valid, internal, multipath
      Community: 11404:993 11404:4000 11404:4010
      Originator: 208.76.153.79, Cluster list: 208.76.153.117
cr1-pdx#show ip bgp 208.76.152.9
BGP routing table entry for 208.76.152.9/32, version 562275567
Paths: (3 available, best #1, table Default-IP-Routing-Table)
Multipath: eBGP iBGP
  Not advertised to any peer
  64524
    208.76.153.79 (metric 516) from 208.76.153.116 (208.76.153.116)
      Origin incomplete, metric 10, localpref 200, valid, internal, best
      Community: 11404:800
      Originator: 208.76.153.79, Cluster list: 208.76.153.116
  64524
    208.76.153.79 (metric 516) from 208.76.153.117 (208.76.153.117)
      Origin incomplete, metric 10, localpref 200, valid, internal
      Community: 11404:800
      Originator: 208.76.153.79, Cluster list: 208.76.153.117
  64524
    208.76.153.118 (metric 2050) from 208.76.153.118 (208.76.153.118)
      Origin incomplete, metric 10, localpref 200, valid, internal
      Community: 11404:800
cr1-pdx#

-----Original Message-----
From: cisco-nsp [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of John van Oppen
Sent: Monday, March 31, 2014 2:37 PM
To: 'Vitkovský Adam'; 'Oliver Boehmer (oboehmer)'; cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] interesting ASR 9k bgp multipath issue

It sure was not in this case, it was pretty obviously 50-50 from my traceroute testing

-----Original Message-----
From: Vitkovský Adam [mailto:adam.vitkovsky at swan.sk]
Sent: Monday, March 31, 2014 2:12 PM
To: John van Oppen; 'Oliver Boehmer (oboehmer)'; cisco-nsp at puck.nether.net
Subject: RE: [c-nsp] interesting ASR 9k bgp multipath issue

If I recall correctly the load-sharing should be proportional to the matric so in your case 254:1 in favor of the path with metric 10.


adam

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