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New Member

OSPF route ages

We have 3 Cisco 6509s running OSPF between them. This is essentially our "new" network. The "old" network bolts on to one of the 6509s. The old network inlcudes a couple of 3Com Netbuilder IIs with remote ISDN sites. The old routers use RIP between them. One of the Netbuilders converts RIP to OSPF and this is distributed into the new network.

What I have noticed is that when looking at the OSPF routes on a 6509, the age of every single route can suddenly reset to zero. This can be after a few seconds or minutes or hours - there is no distinct pattern.

I have seen what happens when a single router is powered on at a remote site i.e. this route appears in the route list under OSPF but has a shorter age than the majority.

What could be causing the entire table on all three 6509s to reset to zero. Users do not appear to be experiencing any problem but I am control freak and would like to know what is happening!

1 REPLY
New Member

Re: OSPF route ages

Every time a topology change occurs, the Dijkstra algorithm is re-ran throughout. A new set of OSPF routes in the forwarding table is the result. Also, the LSAs age out after about 30 minutes, but I'm not aware that refreshing those LSAs causes a recalculation of any sort. Some OSPF debug output might help you to correlate the events.

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