RE: prevent loop on ospf link

From: Edwards, Andrew M (andrew.m.edwards@boeing.com)
Date: Thu Jan 22 2004 - 23:27:45 GMT-3


David,

As far as I can see from what you have provided here there is not a
loop. It looks like you have equal cost paths in OSPF from r5/r6 to the
next hop in BGP to network 191.10.1.1. The trace you are seeing is
correct for load-balancing in OSPF. I think that the timeouts are
related to something else on the simulation network.

Are you having any other issues in the 'frame cloud'?

Andy

-----Original Message-----
From: David Deng [mailto:glend_99@yahoo.com]
Sent: Wednesday, January 21, 2004 10:51 PM
To: ccielab@groupstudy.com
Subject: prevent loop on ospf link

Hi Group,

Have diffuculty on preventing the loop.
Please help, let me know if any information is
missing.

    136.10.56..x
     SWa---r5 -----|
      | |------r2------r1---191.10.1.1
     SWb---r6 -----|

--------------------------------------
swa and swb have trunk link in betwwen
r5 directly connect to SWa vlan 56 in area 3
r6 directly connect to SWb vlan 56 in area 3
link between r2 to r5/r6 is FR multipoint in Area 0
---------------------------------------------

on Swa :

ping 191.10.1.1 will have missed some of the ping . 3550-A#trace
191.10.1.1

Type escape sequence to abort.
Tracing the route to 191.10.1.1

  1 136.10.56.5 4 msec
    136.10.56.6 0 msec
    136.10.56.5 0 msec
  2 *
    136.10.100.2 104 msec *
  3 136.10.12.1 108 msec * 104 msec

SW-A#sh ip route 191.10.1.1
Routing entry for 191.10.1.0/24
  Known via "bgp 65251", distance 200, metric 0
  Tag 100, type internal
  Last update from 136.10.2.2 00:30:29 ago
  Routing Descriptor Blocks:
  * 136.10.2.2, from 136.10.2.2, 00:30:29 ago
      Route metric is 0, traffic share count is 1
      AS Hops 1

SW-A#sh ip route 136.10.2.2
Routing entry for 136.10.2.2/32
  Known via "ospf 100", distance 110, metric 66, type
inter area
  Last update from 136.10.56.6 on Vlan56, 00:20:56 ago
  Routing Descriptor Blocks:
    136.10.56.5, from 136.10.5.5, 00:20:56 ago, via
Vlan56
      Route metric is 66, traffic share count is 1
  * 136.10.56.6, from 136.10.6.6, 00:20:56 ago, via
Vlan56
      Route metric is 66, traffic share count is 1

SW-A#

Thanks,
David

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