Frame Configuration (Cont.)

PVC Switching Configuration Example

You can configure your router as a dedicated, DCE-only Frame Relay switch. Switching is based on DLCIs. The incoming DLCI is examined, and the outgoing interface and DLCI are determined. Switching takes place when the incoming DLCI in the packet is replaced by the outgoing DLCI, and the packet is sent out the outgoing interface.

In Figure 31, the router switches two PVCs between serial interfaces 1 and 2. Frames with DLCI 100 received on serial 1 will be transmitted with DLCI 200 on serial 2.

Figure 31 PVC Switching Configuration

The following example shows one router with two interfaces configured as DCEs. The router switches frames from the incoming interface to the outgoing interface on the basis of the DLCI alone.

Configuration for Router A

frame-relay switching

interface Serial1

 no ip address

 encapsulation frame-relay

 keepalive 15

 frame-relay lmi-type ansi

 frame-relay intf-type dce

 frame-relay route 100 interface Serial2 200

 frame-relay route 101 interface Serial2 201

 clockrate 2000000

!

interface Serial2

 encapsulation frame-relay

 keepalive 15

 frame-relay intf-type dce

 frame-relay route 200 interface Serial1 100

 frame-relay route 201 interface Serial1 101

 clockrate 64000

Pure Frame Relay DCE Example

Using the PVC switching feature, it is possible to build an entire Frame Relay network using routers. In Figure 32, router A and router C act as Frame Relay switches implementing a two-node network. The standard Network-to-Network Interface (NNI) signalling protocol is used between router A and router C.

The following example shows a Frame Relay network with two routers functioning as switches and standard NNI signalling used between them.

Figure 32 Frame Relay DCE Configuration

Configuration for Router A

frame-relay switching

interface serial 1

 no ip address

 encapsulation frame-relay

 frame-relay intf-type dce

 frame-relay lmi-type ansi

 frame-relay route 100 interface serial 2 200

!

interface serial 2

 no ip address

 encapsulation frame-relay

 frame-relay intf-type nni

 frame-relay lmi-type q933a

 frame-relay route 200 interface serial 1 100

 clockrate 2048000

!

Configuration for Router C

frame-relay switching

!

interface serial 1

 no ip address

 encapsulation frame-relay

 frame-relay intf-type dce

 frame-relay route 300 interface serial 2 200

!

interface serial 2

 no ip address

 encapsulation frame-relay

 frame-relay intf-type nni

 frame-relay lmi-type q933a

 frame-relay route 200 interface serial 1 300

!