OSPF adjacency

[vinamranfs1]

we have connected 2 routers with serial link and configured OSPFv2 on them , the routers have established neighbourship

On the way of establishing adjacency the routers when in the EXSTART stage select the master and slave routers.

Now why is that only master sends the request (LSR) for the database but the slave doesn't and both routers get their database updated and send each other LSACK, (the other router doesn't even sends the request for the database). I have checked the packet capture and their is no field available in the OSPF header which notifies the router that it has to send database without the request.

[Peter Paluch]

Hi,

Now why is that only master sends the request (LSR) for the database but the slave doesn't and both routers get their database updated and send each other LSACK, (the other router doesn't even sends the request for the database).

If you have not missed any packet in the capture and its analysis then this must be because one of the routers simply did not have anything to request from the other. During the EXCHANGE phase when the routers sent DBD packets to each other, they must have found out that the router you call the "master" is missing some of the link state database entries that the "slave" knows about, while the "slave" already knows everything what the "master" knows, and so it did not send any requests itself.

Regardless of the master and slave role, during synchronization, any router out of the two can send LSRs. Master and slave role determine who is allowed to send new DBDs with incremented sequence numbers, and who is only allowed to respond to a DBD with its own DBD and the same sequence number.

Best regards,
Peter