Configuring Frame Relay subinterfaces

Frame Relay provides main interfaces and subinterfaces. A subinterface is a logical interface. It can be configured with protocol addresses and virtual circuits. One physical interface can include multiple subinterfaces. The subinterfaces and main interfaces can all be configured with virtual circuits to connect to peer devices.

Frame Relay subinterfaces include the following types:

• Point-to-point (P2P) subinterface—A P2P subinterface connects to a single peer device.

• Point-to-multipoint (P2MP) subinterface—A P2MP subinterface connects to multiple peer devices. A P2MP subinterface can be configured with multiple virtual circuits. An address-to-DLCI map can be configured for each virtual circuit and its connected peer network address. Address-to-DLCI maps can be dynamically configured through InARP or manually configured.

The methods of configuring a virtual circuit and address-to-DLCI map for P2P subinterfaces and P2MP subinterfaces have the following differences:

• P2P subinterface—Because a P2P subinterface has only one peer address, the peer address is determined when a virtual circuit is configured for the subinterface. You cannot configure static address-to-DLCI maps or enable InARP for a P2P subinterface.

• P2MP subinterface—For a P2MP subinterface, a peer address can be mapped to the local DLCI through static address-to-DLCI maps or InARP. To enable InARP for dynamic address mapping on a P2MP subinterface, you only need to enable InARP on the main interface. If static address-to-DLCI maps are needed, you must configure a static address-to-DLCI map for each virtual circuit.

To configure a Frame Relay subinterface: