I am busy redesigning my OSPF network to break it up into different areas and use route summarization to reduce the size of my LSDB and then setup MPLS. It is a rather large network with a thousand+ routers on the backbone area(Hence the need to redesign this).
I have come across an issue which I am trying to figure out a way around. An example area which I am creating has 2 connections to the backbone, so 2 ABRs. I configure summary routes in each of the ABRs, and everything seems to work nicely.
The problem comes in when some link between 2 routers in the middle of the area goes down. Now, the summarized routes get distributed from both ABRs as normal, and only the lowest cost route gets used by the backbone. So the backbone only ends up with the one path to the summarized route towards one of the ABRs. This leaves the other side of the area isolated from the network, because the backbone routes all requests to the entire supernet, to the one ABR, and some of the routers are on the other side of the link that is down, from the ABR where the backbone is routing the supernet to
Is there a best practice way to get around this? How do people handle this situation?
Please let me know if my description is not clear enough.