Configuring a frame relay subinterface
Frame relay offers main interface and subinterface. The subinterface is of logical structure, which can be configured with protocol address and virtual circuit. One physical interface can include multiple subinterfaces, which do not exist physically. However, for the network layer, the subinterface and main interface make no difference and both can be configured with virtual circuits to connect to remote devices.
The subinterfaces of frame relay include the following types:
Point-to-point (P2P) subinterface.
Point-to-multipoint (P2MP) subinterface.
A P2P subinterface connects a single remote device and a P2MP subinterface connects multiple remote devices. A P2MP subinterface can be configured with multiple virtual circuits, each of which sets up an address map with its connected remote network address to distinguish different connections. Address maps can be manually set up, or dynamically set up by InARP or IND.
The methods to configure a virtual circuit and address map for P2P subinterfaces and P2MP subinterfaces are different, as follows:
P2P subinterface—Because only one peer address exists for a P2P subinterface, the peer address is determined when a virtual circuit is configured for the subinterface. You do not need to configure dynamic or static address mapping for P2P subinterface.
P2MP subinterface—For a P2MP subinterface, a peer address can be mapped to the local DLCI through static address mapping or InARP. The InARP or IND configuration only needs to be configured on the main interface. If static address mapping is required, it is necessary to set up static address map for each virtual circuit.
To configure a frame relay subinterface:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Create a subinterface and enter subinterface view. | interface interface-type interface-number.subnumber [ p2mp | p2p ] | By default, a frame relay subinterface operates in p2mp mode. |
3. Configure a virtual circuit on the frame relay subinterface. | On a frame relay subinterface, virtual circuits must be created manually and be identical to those created at the DCE end. | |
4. Configure address mappings. | Optional for a P2P subinterface. Required for a P2MP subinterface. |