OSPF loosing adjaceny

Unanswered Question
Jun 27th, 2009

I have two routers connect through FR and F0/0. I change the bandwidth on the FR to 100000 to load balance between the two links. And also the hello to 2 sec and dead timer to 8 sec on both. But ever since then the adjacency on the two link keep going up and down..please whats the reason for this.

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Giuseppe Larosa Sat, 06/27/2009 - 23:43

Hello Just,

is this a lab or a production environment?

In any case if there is live traffic once you make the FR link to have equal cost half traffic is sent out it.

Not all Cisco platforms have hidden system queue to protect routing protocol messages.

If so they have to compete with user traffic with same probability to be discarded if the link is saturated.

So you could have a saw traffic graph:

first the adjacency forms the traffic arrives then the adj is lost and again.


I see you say both links have the OSPF adjacencies going up and down try to use higher timers and see if this change the behaviour

Hope to help


Just Kennie Sun, 06/28/2009 - 00:45

Its a Lab with no traffic at all. My surprise is that the adjaceny keep going up and down below . Need to know why before I can increase the timer, because the Yask is actually to reduce the time. Please let me know why.

Giuseppe Larosa Sun, 06/28/2009 - 02:33

Hello Just,

>> Need to know why before I can increase the timer,

use the debug ospf commands or simply look at the log of the two routers to find the weak side.

if you are using dynamips and GNS3 be aware that emulation has performance limits that are not present in real routers.

Hope to help



This Discussion