In the figure, router A has two point-to-point subinterfaces. The s0/0.110 subinterface connects to router B and the s0/0.120 subinterface connects to router C. Each subinterface is on a different subnet. To configure subinterfaces on a physical interface, the following steps are required:

• Configure Frame Relay encapsulation on the physical interface using the encapsulation frame-relay command
• For each of the defined PVCs, create a logical subinterface

  router(config-if)#interface serial number.subinterface-number {multipoint | point-to-point}

To create a subinterface, use the interface serial command. Specify the port number, followed by a period (.), and then by the subinterface number. Usually, the subinterface number is chosen to be that of the DLCI. This makes troubleshooting easier. The final required parameter is stating whether the subinterface is a point-to-point or point-to-multipoint interface. Either the multipoint or point-to-point keyword is required. There is no default. The following commands create the subinterface for the PVC to router B:

routerA(config-if)#interface serial 0/0.110 point-to-point

If the subinterface is configured as point-to-point, then the local DLCI for the subinterface must also be configured in order to distinguish it from the physical interface. The DLCI is also required for multipoint subinterfaces for which Inverse ARP is enabled. It is not required for multipoint subinterfaces configured with static route maps. The frame-relay interface-dlci command is used to configure the local DLCI on the subinterface

router(config-subif)#frame-relay interface-dlci dlci-number

Lab Activity Lab Exercise: Configuring Frame Relay Subinterfaces In this lab, the student will configure three routers in a full-mesh Frame Relay network.

       

Web Links Configuring Frame Relay Subinterfaces http://www.cisco.com/en/US/ tech/tk713/tk237/technologies_configuration_ example09186a008009421e.shtml