BGP OSPF redistribution.

1. By default, BGP only redistribute ospf network type internal. To redistribute other type of ospf network, you need to add to the redistribution
redistribute ospf 1 ------ Only internal (intra and inter-area) routes
redistribute ospf 1 match external ---- Only external type 1 and 2 route
redistribute ospf 1 match internal external 2 --- only internal and external type 2
redistribute ospf 1 match nssa-external 1 ---- Only nssa-external type 1.

2. By default, iBGP redistribution into IGP is disabled.
Issue the bgp redistribute-internal command under router bgp process in order to enable redistribution of iBGP routes into IGP.

3. BGP and OSPF router-id
If BGP synchronization is enabled, there must be a match for the prefix in the IP routing table in order for an internal BGP (iBGP) path to be considered a valid path.

4. Link for tips. 911network.