Configuring L1 Routers

To configure a switch to operate as a level 1 IS-IS router, do the following:

  1. Prepare the IP interfaces that will support level 1 IS-IS routing as follows:
    1. Add an IPv4 or IPv6 address.
    2. Enable IP or IPv6 forwarding.
  2. Create the IS-IS routing process, which is also called an area, using the following command:
    create isis area area_name
  3. Configure the routing process to serve as a L1-only router using the following command:
    configure isis area area_name is-type level [1 | 2 | both-1-and-2]

    Specify 1 for the level option using the following command:

  4. Add an IS-IS area level-1 address to the router using the following command:
    configure isis area area_name add area-address area_address
  5. Add IS-IS-eligible interfaces to the area using the following command:
    configure isis add [vlan all | {vlan} vlan_name] area area_name {ipv4 | ipv6}
    An IS-IS-eligible interface is one that already has the appropriate IP address type (IPv4 or IPv6) address assigned to it.
  6. The default IS-IS system ID is the switch MAC address. If you want to change the default IS-IS system ID, using the following command:
    configure isis area area_name system-id [automatic | system_id]
  7. Enable the IS-IS router using the following command:
    enable isis {area area_name}
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