Configuring Frame Relay Using Subinterfaces

Subinterfaces enable you to solve split-horizon problems and to create multiple PVCs on a single physical connection to the Frame Relay cloud.

Router(config)#int s 0/0
Router(config-if)#encapsulation frame-relay ietf	Sets the Frame Relay encapsulation type for all subinterfaces on this interface
Router(config-if)#frame-relay lmi-type ansi	Sets the LMI type for all subinterfaces on this interface
Router(config-if)#no ip address	Ensures there is no IP address set to this interface.
Router(config-if)#no shut
Router(config-if)#interface s 0/0.102 point-to-point	Creates a point-to-point subinterface numbered 102
Router(config-subif)#ip address 192.168.10.1 255.255.255.0	Assigns an IP address to the subinterface
Router(config-subif)#frame-relay interface-dlci 102	Assigns a DLCI to the subinterface
Router(config-subif)#int s 0/0.103 point-to-point	Creates a point-to-point subinterface numbered 103
Router(config-subif)#ip address 192.168.20.1 255.255.255.0	Assigns an IP address to the subinterface
Router(config-subif)#frame-relay interface-dlci 103	Assigns a DLCI to the subinterface
Router(config-subif)#exit
Router(config-if)#exit
Router(config)#

Note:

There are two types of subinterfaces:

• Point-to-point, where a single PVC connects one router to another and each subinterface is in its own IP subnet.

• Multipoint, where the router is the middle point of a group of routers. All other routers connect to each other through this router and all routers are in the same subnet.

Note:

Use the no ip split-horizon command to turn off split-horizon commands on multipoint interfaces so that remote sites can see each other.