Issue 1 Solution
It is important that you understand the error message during attempts to troubleshoot flood war messages. The messages appear differently on the origination and flush routers. For this reason, it is crucial to focus on the LSA type for which the flood war message is reported, as each LSA type is troubleshot differently.
Here is an example snippet of the OSPF flood war message:
%OSPF-4-FLOOD_WAR: Process 1 re-originates LSA ID 172.16.254.25 type-2 adv-rtr
172.16.253.1 in area 0
%OSPF-4-FLOOD_WAR: Process 1 flushes LSA ID 172.16.254.25 type-2 adv-rtr
172.16.253.1 in area 0
Here are the message components described:
- Process – This is the OSPF process that reports the error.
- re-originates or flushes – This indicates whether this router originates or flushes the LSA.
- LSA ID – This is the LSA ID for which the flood war is detected.
- Type – This is the LSA type.
Note: The flood war for every LSA has a different root cause.
- adv-rtr – This is the Advertising router that originates the LSA.
- Area – This is the area to which the LSA belongs.
Type-2 LSAs
Note: Refer to RFC 2328 (Chapter 13.4, Case 3) for additional information if the flood war is printed for a Type-2 LSA.
If a router receives a Type-2 network LSA whose LSA ID is the same as the IP address for one of the interfaces that are associated with that router, then the router should flush the LSA. The root cause in this scenario is the duplicate IP addresses on the origination and flush routers.
In order to resolve this issue, reconfigure the IP address on one of the interfaces or shutdown the interface that has the duplicate IP address.
Note: This check for duplicate IP addresses is performed on interfaces that are down as well. The interface must be in admin-down mode in order to bypass the check. In some corner cases, the flood war is also reported for an administratively shut down interface, so the permanent solution is to remove the duplicate IP addresses in the network.