2 nodes are connected using port channel. Initially OSPF settled in two nodes. When I shut and no shut the port channel interface, OSPF in 1st node is stuck in EXSTART state. In 2 nd node, OSPF is in FULL state because it started receiving hello packets from 1st node within dead interval. While debugging, I came to know that, 1st node is sending Database Description packet(DDP) at ExStart state. But 2nd node is not receiving that Database description packet. In some sites, they had mentioned, MTU size may differ. But In my case, MTU is also same. So what can be the other resons for this? Why DDP is not received at 2nd node.?
Thanks in Advance...
MTU mismatch could be the primary cause for an OSPF router to be in EXSTART state. But as you mentioned, you have already verified the MTU values on both interfaces, try to take ospf debug logs on Router which is stuck in EXSTART state.
It could be a bug with respect to device. Check if the issue replicates, in the sense, does the EXSTART state stay the same, when you shut and no shut the interface on Router which is stuck in EXSTART state.