Advanced OSPF Notes
Always check your OSPF neighbors. I had a problem injecting a default route into NSSA totally stub area, and I figured out it was a problem of OSPF network types.R3 and R4 were not already OSPF Neighbors. They are connected through Frame relay. R3 interface is “point-to-point” OSPF network type. R4 however, has interface ser0/0 in “NBMA” OSPF Network type.I corrected the network type under ser0/0 of R4 and it works
– Redistributed routes that are coming from area 0 are not
injected into NSSA (neither into stub areas).This
is a nice post by Peter Paluch about interpreting OSPF database.
Show ip ospf database
NSSA and default route
The default behaviour in NSSA is: no default route is injected by the NSSA ABR:
show ip route
Routes are inserted normally.
Use of “default-information-originate” on an NSSA ABR to inject a default route into NSSA:
show ip OSPF database
We know that, an NSSA ASBR injects LSA7 into NSSA. Why is R3 an ASBR?
RIB on R4:
Use of “no-summary” on NSSA ABR to inject a default route into NSSA:
No-summary is set on R3. OSPF database on R4 has shrinked:
RIB on R4:
Adsense black background: