IP routing configuration examples 143

Not So Stubby Areas (NSSA) Similar to stub areas, the not so stubby area (NSSA) can also prevent the flooding of AS-External Link State advertisements into the NSSA by replacing them with a default route. However, NSSA can also import small stub (non-OSPF) routing domains into OSPF. This allows the NSSA to import external routes, such as RIP routes, and then advertise these routes throughout the network.

External routing information is imported into NSSA by using type 7 LSAs. These LSAs are translated at the NSSA boundary into LSA type 5. The N/P bit in the type 7 LSA Options field indicates whether the type 7 LSA must be translated. Only those LSAs with the N/P-bit set are translated.

The NSSA configuration example illustrated below demonstrates a Nortel Ethernet Routing Switch 5500 Series configured as a NSSA ASBR router.

NSSA configuration example

To configure the example illustrated above, follow this procedure:

Step Action

1Configure router R1.

a.Configure the RIP interface on R1.

Configure port 1/20 as a brouter port in VLAN 100 and enable RIP on this interface.

5530-24TFD(config)# interface fast 1/20

5530-24TFD(config-if)# brouter port 1/20 vlan 100 subnet 20.1.1.2/30

5530-24TFD(config)# router rip

5530-24TFD(config-router)# network 20.1.1.2

b.Enable RIP globally and configure the RIP version 2 interface.

5530-24TFD(config)# router rip enable

Nortel Ethernet Routing Switch 5500 Series

Configuration-IP Routing Protocols

NN47200-503 03.01 Standard

5.127 August 2007

Copyright © 2005-2007, Nortel Networks

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Nortel Networks NN47200-503 manual Enable RIP globally and configure the RIP version 2 interface, Nssa configuration example