# Enabling IS-IS for IP Routing

When enabling IS-IS, you must create an IS-IS routing process and assign it to specific interfaces rather than to networks. You can specify only a single IS-IS process per router.

To enable IS-IS routing, enter Global Configuration mode, and follow this procedure:

1. Specify an IS-IS process for IP. In this example, floor12 is specified as the tag name.
   host1(config)#router isis floor12

   The router is now in Router Configuration mode.

2. Configure a Network Entity Title (NET) for the routing process that specifies the ISO network address.
   host1(config-router)#net 47.0010.0000.0000.0000.0001.0001.1111.1111.1111.00
3. Enter Interface Configuration mode, and specify the interface that you want to actively route IS-IS.
   host1(config)#interface atm 2/0
4. Specify the IS-IS process to apply to the interface. Use the same tag name that you specified with the router isis command.
   host1(config-if)#ip router isis floor12

   You can repeat Steps 3 and 4 to apply the IS-IS process to multiple interfaces.

ip router isis

- Use to configure an IS-IS routing process on an IP interface.
- Before the IS-IS router process is useful, you must assign a NET with the net command, and enable some interfaces with IS-IS.
- Use the tag parameter to specify a meaningful name for a routing process. It must be unique among all IP routing processes for a given router. If you choose not to specify a tag name, a null tag is assumed, and the process is referenced with a null tag. Use the same tag name for ip router isis as you did for the router isis command.
- Example
  host1(config-if)#ip router isis floor12
- Use the no version to disable IS-IS for IP on the interface.
- See ip router isis

net

- Use to configure a NET for a specified routing process. The NET defines the ISO address and consists of an area address or ID, a system ID, and a selector.
- You must configure a minimum of one NET.
- You can have a maximum of three NETs per router.
- You can manually add multiple area IDs by adding multiple NETs with the same system ID.
- There is no default value; net must be configured for an IS-IS process to start.
- Multiple NETs can be temporarily useful when there has been a network reconfiguration where either multiple areas are merged, or one area is in the process of being split into more areas. Multiple area addresses enable you to renumber an area slowly, without needing to set aside time to renumber areas all at once.
- When you use IS-IS to do IP routing only, a NET must be configured to instruct the router about its system ID and area ID.
- Example—The following commands configure a router with the area ID 47.0005.80ff.f800.0000.0001.0001 and the system ID 0000.0c11.1111. The last byte of the NET is the N-selector byte and is always 0.
  host1(config-router)#net 47.0010.0000.0000.0000.0001.0001.1111.1111.1111.00
- Use the no version to remove a specific NET. Remember that you must specify the NET. The last NET cannot be removed.
- See net

router isis

- Use to enable the IS-IS routing protocol and to specify an IS-IS process for IP.
- Specify only one IS-IS process per router.
- Use the tag parameter to specify a meaningful name for a routing process. If you choose not to specify a tag name, a null tag is assumed, and the process is referenced with a null tag.
- Example
  host1(config)#router isis floor12
- Use the no version to disable IS-IS routing.
- See router isis

## Summary Example

host1(config)#router isis floor12 host1(config-router)#net 47.0010.0000.0000.0000.0001.0001.1111.1111.1111.00 host1(config-router)#exit host1(config)#interface atm 2/0 host1(config-if)#ip router isis floor12 host1(config-router)#exit host1(config-if)#interface atm 2/1 host1(config-if)#ip router isis floor12