OSPF Flood War

[Frank Beckers]

ello everybody,

I have the following problem on a WS - C3850-12S . The log is always the following :

% OSPF - 4 - FLOOD_WAR : Process 100 re - originates LSA ID 10.250.250.53 type - 2 adv - rtr 10.255.255.59 in area 0

The funny thing is that both addresses are on the router . The 10.250.250.53 is the transport network to the next router and the 10.255.255.59 is the Loopback0

Does anyone have an idea where the problem comes ?

Best regards

Frank

[Peter Paluch]

Frank,

It seems that this router feels necessary to re-originate the LSA-2 for the network in which its interface with the IP address 10.250.250.53 resides. Obviously, 10.250.250.53 considers itself to be a Designated Router and so it needs to originate an LSA-2 for this network. However, someone else is originating an LSA-2 with the same identifier, namely, 10.250.250.53, and this router tries to "counteract" it by asserting its own LSA-2.

You definitely need to check for these possible causes:

• On the link between the 10.250.250.53 and the neighboring router, verify whether there is exactly one DR and one BDR
• Verify whether these two routers have unique OSPF Router IDs (show ip ospf, for example)
• Verify whether anywhere else in the network there is a router that uses the same IP address 10.250.250.53 (it can be anywhere, not just on this link)
• Verify whether anywhere else in the network there is a router whose Router ID is equal to 10.255.255.59.

This might be a daunting task to find...

Best regards,
Peter

[Frank Beckers]

Ok Peter, thanks for the tip,

We have now assigned the new Router ID . Error remains . Nor do we find now in IP network . But we are going to change the transport network and see whether the error is still there tomorrow . Our guess is that this transport network may nevertheless already is somewhere in -use . I will report.

Best regards Frank