OSPF stability

Gngogh

Hi, i am trying to understand what is best to use on a OSPF network, is it to configure manualy the RID or to use Loopback int's.
I know that we can ping the loopback in case of troubleshooting, but if we do, it means that we can ping physical interfaces as well. I am a bit confused here...

OfWolfAndMan

1. Manual Router ID
2. Highest IP configured loopback
3. Highest IP of physical interface

^In that order.

Gngogh

thanks for your reply, i understand the ospf RID election process. what i dont understand, is what is best to use for OSPF stability is it a manualy configured RID or Loopback interface, and why???

networker050184

Best practice is to hard code it to a loopback interface.

lrb

Remember that the OSPF router ID is just a 32-bit numbered expressed in dotted quad format (like an IP address) so it can actually be anything you want it too. It's purpose is to uniquely identify each router in the LSDB. You can set R1's router ID to 0.0.0.1 and R2's to 0.0.0.2 and it will have no negative effect even though these are not routable.

In practice however, as networker050184 said you would use the IP address on a Loopback interface as the router ID. In a lot of cases, the loopback used as the OSPF router ID will be the MPLS router ID which does need to be a routable address advertised by OSPF