Configuring Frame Relay

Once you understand how frame relay works, the mechanics of configuration are not very difficult. There are some interesting concepts, such as subinterfaces, that may be new to you; we'll cover those in detail here.

Basic Frame Relay with Two Nodes

Figure 22-10 shows a simple two-node frame-relay network. Router A is connected to Router B using frame relay over a T1. The port speed is 1.536 Mbps, the CIR is 512 Kbps, and the burst rate is 2X (1,024 Kbps).

Two-node frame-relay network

Figure 22-10. Two-node frame-relay network

The first step in configuring frame relay is to configure frame-relay encapsulation. There are two types of frame-relay encapsulation: cisco and ietf. The default type is cisco, which is configured with the encapsulation frame-relay command:

interface Serial0/0
encapsulation frame-relay

The ietf type is configured with the encapsulation frame-relay ietf command. ietf frame-relay encapsulation is usually used only when connecting Cisco routers to non-Cisco devices.

Once you've configured frame-relay encapsulation, and the interface is up, you should begin seeing LMI status messages. If the PVC has been provisioned, you can see it with the show frame-relay PVC command:

Router-A#sho frame pvc

PVC Statistics for interface Serial0/0 (Frame Relay DTE)

              Active     Inactive      Deleted       Static
  Local          0            0            0            0
  Switched       0            0            0            0
  Unused         0            1            0            0

DLCI = 102, DLCI USAGE = UNUSED, PVC STATUS = INACTIVE, ...

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