Configuring summary addresses

You can configure summary addresses to aggregate IS-IS route information. Summary addresses can enhance performance by reducing the size of the Link State database, reducing the amount of data the device needs to send to its neighbors, and reducing the CPU cycles used for IS-IS. The following task configures a summary address of 10.1.0.0 with a mask of 255.255.0.0 for Level 1 and Level 2 routes.

About this task

Procedure

Enter the configure terminal command to access global configuration mode.
```
device# configure terminal
```
Enter the router isis command to enter IS-IS router configuration mode and enable IS-IS on the device.
```
device(config)# router isis
```
Enter the address-family ipv4 unicast command to enable ISIS address-family IPv4 unicast configuration mode.
```
device(config-isis-router)# address-family ipv4 unicast
```
Enter the summary-address command with the level-1 and level-2 parameters, specifying an IPv4 address and network mask to configure a summary address and network mask for Level 1 and Level 2 routes.
```
device(config-router-isis-ipv4u)# summary-address 10.1.0.0 255.255.0.0 level-1 level-2
```

Example

The following example configures a summary address of 10.1.0.0 with a mask of 255.255.0.0 for Level 1 and Level 2 routes.

device# configure terminal
device(config)# router isis
device(config-isis-router)# address-family ipv4 unicast
device(config-router-isis-ipv4u)# summary-address 10.1.0.0 255.255.0.0 level-1 level-2