I have a network that sits on our core and is native to the OSPF process. It's a class C address - 172.27.12.0.
I have two ABRs that are running both OSPF and BGP and peering with the same distant-end router. Both ABRs advertise summary routes for 172.27.0.0/16 to the peer.
That peer router receives a metric of 6 from one ABR and a metric of 4 from the other for 172.27.0.0/16. Furthermore, if I check the local BGP table on both ABRs for that network (sh ip bgp 172.27.12.0), again, one ABR shows a metric of 4 and the other a metric of 6 for the summary routes they're advertising.
Neither ABR has any route maps configured nor is any sort of policy routing being implemented. So, these metrics seem to be default metrics.
The ABR that is advertising a BGP cost of 6 for 172.27.12.0 has an OSPF cost of 0 because it's a directly connected network. And the ABR that is advertising a BGP cost of 4 for that same network has an OSPF cost of 5.
Question: How was the metric determined by each ABR for the route it advertised to its peer through BGP? Why the disparity?
Thanks
