How to Configure OSPF NSSA Totally Stub

OSPF Stub Areas

1. Stub Area - No Type 4 ASBR or 5 AS-external LSAs allowed.
2. Totally Stub Area - No Type 3 Summary, 4 ASBR or 5 External LSAs allowed except the default summary route.
3. NSSA (Not-So-Stubby Area) - No Type 5 AS-external LSAs allowed,
but Type 7 LSAs that convert to Type 5 at the NSSA ABR can traverse.
4. NSSA Totally Stub - No Type 3 Summary LSA, 4 ASBR or 5 External LSAs except the default summary route,
but Type 7 LSAs that convert to Type 5 at the NSSA ABR are allowed.



How to Configure OSPF NSSA Totally Stub:

CONFIGURE:
R1:
conf t
router ospf 1
network 10.10.12.0 0.0.0.255 area 0
redistribute connected subnets
end
wr

R2:
conf t
router ospf 1
network 10.10.12.0 0.0.0.255 area 0
network 10.10.23.0 0.0.0.255 area 1
end
wr

R3:
conf t
router ospf 1
network 10.10.23.0 0.0.0.255 area 1
redistribute connected subnets
end
wr

Configure Area 1 to be a NSSA Totally Stub:
R2:
conf t
router ospf 1
area 1 nssa no-summary
end
wr

R3:
conf t
router ospf 1
area 1 nssa
end
wr

VERIFY:
show ip ospf neighbor
show ip route ospf
show ip ospf database
clear ip ospf process

REFERENCES:

Types of OSPF Areas

OSPF Not-So-Stubby Area (NSSA)

How OSPF Injects a Default Route into a Not So Stubby Area

What Are OSPF Areas and Virtual Links?

OSPF Database Explanation Guide

#cisco #ccna #ccnp #ccie

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