7.2 Configuring X.25
7.2.4 Configuring X.25 PVCs
As you did when configuring X.25 SVCs, use the encapsulation x25 command to specify the encapsulation style to be used on the serial interface:

Router(config-if)#encapsulation x25 [dte | dce]

As you did when configuring X.25 SVCs, use the x25 address command to define the local router X.121 address (one address per interface). The value specified must match the address designated by the X.25 PDN:

Router(config-if)#x25 address x.121-address

Instead of establishing an SVC with the x25 map command, you can establish a PVC. PVCs are the X.25 equivalent of leased lines; they are never disconnected. You do not need to configure an address map before defining a PVC; an encapsulation PVC implicitly defines a map. To establish an encapsulation PVC, enter the x25 pvc command in interface configuration mode. Command syntax follows:

Router(config-if)#x25 pvc circuit protocol address

[protocol2 address2]* x.121-address [options]

Table describes the x25 pvc command.

Multiple protocols can be routed on the same PVC. Multiple circuits can also be established on an interface by creating another PVC.

Before configuring X.25 parameters, you must enter interface configuration mode and assign a higher-layer address, such as an IP address to the interface.

Configuring X.25 PVC Examples

The example in Figure demonstrates how to use the PVC to exchange IP traffic between the central-site and branch office router.

In this example, the public network has established a PVC through its network, connecting PVC number three to PVC number four. On the central-site router, a connection is established between the central-site router and the branch-office IP address, 10.60.8.2. On the branch-office router, a connection is established between the branch-office and central-site IP address, 10.60.8.1.

Example shows the central-site PVC configuration for the network shown in Figure .

Example shows the branch-office PVC configuration for the network shown in Figure .

Lab Activity
  Because an X.25 network is not available, you will first configure a router to act as a X.25 switch. Once the switch is configured, you will configure two routers to interface with the X.25 network. Use X.25 PVCs to create a functional link between the two routers. The branch router is a stub network, so configure a default route on the branch router side and a static route on the central router side.