OSPF Default Routing

• Create a default route into a specific area
• Create a default route into the entire OSPF domain
• Default-information originate
  • Creates a default route into OSPF, external Type 2 route, using a Type 5 LSA with metric 20
  • default-information originate (always) metric 30 metric-type 1 route-map NAME
    
    • Default metric 20
    • Default metric-type 2
      • metric-type 1 cost can be changed
        
      • metric-type 2 cost can’t be changed
  • The metric-type defines LSA is Type 1 External or Type 2 External (default)
  • Route-map is used for tracking networks. If Route-map condition is met, default route is advertized.

Gateway of last resort is 2.2.2.2 to network 0.0.0.0

1.0.0.0/32 is subnetted, 2 subnets
O IA 1.1.1.1 [110/21] via 2.2.2.2, 00:00:06, FastEthernet0/0
O IA 1.1.0.1 [110/21] via 2.2.2.2, 00:00:06, FastEthernet0/0
2.0.0.0/24 is subnetted, 1 subnets
C 2.2.2.0 is directly connected, FastEthernet0/0
3.0.0.0/24 is subnetted, 1 subnets
C 3.3.3.0 is directly connected, Loopback1
20.0.0.0/32 is subnetted, 1 subnets
O IA 20.20.20.20 [110/11] via 2.2.2.2, 00:00:06, FastEthernet0/0
10.0.0.0/24 is subnetted, 1 subnets
O IA 10.10.10.0 [110/20] via 2.2.2.2, 00:00:08, FastEthernet0/0
O*E2 0.0.0.0/0 [110/1] via 2.2.2.2, 00:00:08, FastEthernet0/0
R3#

Default route to Stub Areas

• Use the default route instead of more specific
• The ABR injects the default route into an area.
• ABR creates a default route using a Type 3 LSA and floods that into the stub area
• ABR do not flood Type 5 LSA into the stub area
• ABR do not flood any other Type 3 LSA into the stub area
• Default route has a metric of 1