Core Issue
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.
Resolution
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.
For information on configuring IS-IS over Frame Relay, refer to IS-IS Network Types and Frame Relay Interfaces.
How are Neighbors Connected
Connected via Frame Relay
