i All,
In my network we have OSPF between the routers. All are in area 0. From couple of days we are seeing routing loops for few routers Loopback IP. Suddenly ping will drop to destination router loopback IP (10.10.10.10). When i do traceroute to the loopback then the traffic will loop between router A and router B but traffic to other subnets which are behind router C will not have any issue. it will loop for few mins and fixes itself and after few mins again it will start. when there is a loop I have done traceroute from router B to router C loopback. No issue found but when i do it from A it will just loop. I saw the OSPF route and routing table while its getting loop. It looks good. when it getting loop, i went to router A and checked the routing for 10.10.10.10. it tell its reachable via router B. i go to router B and check routing. It tell its coming from router C. but when we do traceroute. it just loop between router A and router B. So traffic is not getting forwarded to router C from B even we have route in routing table.
Its happening for few hours and it fixes itself and will start after few hours or days. If i clear the OSPF then issue solves but will start after few days. It happens only for loopback due to this we are getting lot of monitoring alerts. Its happening for 6-8 L3 switch's.
Below is the traceroute results.
In real time its not router its L3 swicthes.
