If you configure the redistribution of OSPF into BGP without keywords, only OSPF intra-area

and inter-area routes are redistributed into BGP, by default. You can use the internal keyword

along with the redistribute command under router bgp to redistribute OSPF intra- and inter-area

routes.

Use the external keyword along with the redistribute command under router bgp to redistribute

OSPF external routes into BGP.

-> In order to redistribute all OSPF routes into BGP, we must use both internal and external

keywords. The full command would be (suppose we are using OSPF 1):

redistribute ospf 1 match internal external

Note: The configuration shows match internal external 1 external 2. This is normal because

OSPF automatically appends “external 1 external 2” in the configuration. In other words,

keyword external = external 1 external 2. External 1 = O E1 and External 2 = O E2.