Question

A network engineer redistributes BGP-learned routes into OSPF on an ASBR using the command 'redistribute bgp 65001 subnets'. Users report that when there are two ASBRs advertising the same external prefixes with different internal path costs to reach them, traffic does not always take the path with the lowest total cost to the ASBR. The engineer confirms both ASBRs are advertising the routes. What is the MOST likely reason the internal cost to the ASBR is being ignored in path selection?

Accepted Answer

OSPF redistributes external routes as E2 by default, so only the external metric is considered and the internal cost to the ASBR is used only as a tiebreaker.

Answer

The 'subnets' keyword forces all redistributed routes to become E1, which sums internal and external cost incorrectly.

Answer

BGP routes cannot be redistributed into OSPF without a route map, so the metric is set to infinity.

Answer

OSPF external routes always use the internal cost only, so the issue must be a duplicate router ID on the two ASBRs.