Configuring a summary-address for the NSSA

If you want the ABR that connects the NSSA to other areas to summarize the routes in the NSSA before translating them into type 5 LSAs and flooding them into the other areas, configure an address range summary-address. The ABR creates an aggregate value based on the address range. The aggregate value becomes the address that the ABR advertises instead of advertising the individual addresses represented by the aggregate. You can configure up to 32 ranges in an OSPFv2 area.

1. Enter the configure terminal command to access global configuration mode.
   

   device# configure terminal

2. Enter the router ospf command to enter OSPF router configuration mode and enable OSPFv2 on the device.
   

   device(config)# router ospf

3. Enter the area nssa command, specifying an area and a cost.
   

   device(config-router-ospf-vrf-default-vrf)# area 10.1.1.1 nssa 10

4. Enter the summary-address command, followed by the IP address and mask for the summary route.
   

   device(config-router-ospf-vrf-default-vrf)# summary-address 10.10.1.0	10.10.2.0

The following example configures a summary-address in NSSA 10.1.1.1.

device# configure terminal
device(config)# router ospf
device(config-router-ospf-vrf-default-vrf)# area 10.1.1.1 nssa 10
device(config-router-ospf-vrf-default-vrf)# summary-address 10.10.1.0 10.10.2.0