The OSPF Command for a Stub Area

After designing the addressing scheme for the network, it should be clear which areas, if any, are suitable candidates for configuration as a stub, totally stubby, or not so stubby areas.

NOTE In this age of jargon and complex language, it is refreshing that the industry sense of humor allows such descriptive yet slightly ludicrous terms to have official status.

The syntax for the OSPF router command for a stub area is as follows:

area area-id stub Figure 6-9 illustrates the example configuration that follows.

Figure 6-9 The Configuration of a Stub Area

Figure 6-9 The Configuration of a Stub Area

Example 6-4 shows the creation of a stub area. Note that both the ABR and the internal router share this configuration.

Example 6-4 The Configuration of a Stub Area

Router Nina ospf 100

network 0.0.0.0 255.255.255.255 area 1 area 1 stub Router Jack router ospf 100

network 172.16.20.128 0.0.0.7 area 0 network 172.16.20.8 0.0.0.7 area 1 area 0 range 172.16.20.128 255.255.255.192 area 1 stub

NOTE All OSPF routers inside a stub area must be configured as stub routers. This is because whenever an area is configured as a stub, all interfaces that belong to that area will start exchanging hello packets with a flag that indicates that the interface is a stub. Actually, this is just a bit in the hello packet (E bit) that gets set to 0. All routers that have a common segment must agree on that flag. If they don't, they will not become neighbors, and routing will not take effect.

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