Intermediate System-to-Intermediate System (IS-IS) recognizes networks as either point-to-point or broadcast. On point-to-point networks, point-to-point IS-IS Hellos (IIHs) are exchanged, while on broadcast networks Level 1 or Level 2 LAN IIHs are exchanged. Frame Relay multipoint interfaces are treated as interfaces connected to broadcast networks, and LAN IIHs are sent out. Meanwhile, Frame Relay point-to-point interfaces are treated as interfaces connected to point-to-point networks, and point-to-point IIHs are sent out. When configuring IS-IS over a Frame Relay, the type of Frame Relay interface should match on all routers on a common segment so that the hellos are exchanged successfully.
To configure IS-IS over Frame Relay networks, perform these required steps:
Enable the IS-IS routing protocol on the router by issuing the router isis command in global configuration mode.
Assign a Network Entity Title (NET) address to the router. To configure an IS-IS NET for a Connectionless Network Service Protocol (CLNS) routing process, issue the net command in router configuration mode.
Enable IS-IS routing for IP or CLNS on the interfaces by choosing one of the following procedures:
To configure an IS-IS routing process for IP on an interface, issue the ip router isis command in interface configuration mode.
To configure an IS-IS routing process for International Organization for Standardization (ISO) CLNS on an interface, issue the clns router isis command in interface configuration mode.
Configure the router's interface for Frame Relay. Ensure that the Frame Relay interface type matches on all routers on a common segment. To create a static mapping to allow IS-IS packets to be carried over the Frame Relay network, issue the frame-relay map clns command.