Creating WANs by Using a Cisco Router as a Frame Relay Switch

Creating WANs by Using a Cisco Router as a Frame Relay Switch

You can configure any Cisco router with Cisco IOS Release 11.0 or later and at least two serial interfaces as a Frame Relay switch. Two interfaces are needed because the switch is primarily a data communications equipment (DCE) device and requires two routers to serve as the data terminal equipment (DTE) devices. Because the Frame Relay switch is a DCE-only device, it requires DCE serial cables as well.

The most common way to provide Layer 1 WAN connectivity between routers is to connect a female V.35 DCE cable to a male V.35 DTE cable. In any back-to-back configuration, you need to ensure that one side (DCE) of the link sets clocking. To configure an interface's clock rate, use the clock rate [value] command. Example 2-1 shows how to set the clocking on a serial interface