Configuring a Cisco Router as a Frame Relay Switch

 First we configure R4 as a frame-relay switch with the frame-relay switching command. We then configure the serial interfaces that connect the routers to the frame relay switch . Serial 1/1 connects to R1. The encapsulation frame-relay command tells the serial interface to actually run frame relay. The clock rate has also been configured. The frame-relay intf-type dce command is very important. It tell the router to be the dce device. The frame-relay route interface configuration command is used to route an incoming DLCI to an outgoing interface and corresponding outgoing DLCI. It is also very important. For example frame-relay route 102 interface Serial 1/2 201 under the serial 1/1 means that if a frame enters interface serial 1/1 with DLCI 102 in the frame-relay header, it will be switch out interface serial 1/2 with DLCI 201.

Frame Relay Switch
==================
frame-relay switching
!
interface Serial 1/1
 description R2 Serial
 no ip address
 encapsulation frame-relay
 clockrate 64000
 frame-relay intf-type dce
 frame-relay route 102 interface Serial 1/2 201
 frame-relay route 103 interface Serial 1/3 301
 no shutdown
exit
interface Serial 1/2
 description R2 Serial
 no ip address
 encapsulation frame-relay
 clockrate 64000
 frame-relay intf-type dce
 frame-relay route 201 interface Serial 1/1 102
 no shutdown
exit
interface Serial 1/3
 description R3 Serial
 no ip address
 encapsulation frame-relay
 clockrate 64000
 frame-relay intf-type dce
 frame-relay route 301 interface Serial 1/1 103
 no shutdown
=================================================
Let us test the Frame Relay switch now.

======================================================================================

With this our frame-relay switch is good to go!! Let us test it by running OSPF on it.

R1

==

conf t
int ser 1/0
encapsulation frame-relay
no shut
exit
int ser 1/0.102 point-to-point
ip add 192.168.12.1 255.255.255.252
frame-relay interface-dlci 102
exit
int ser 1/0.103 point-to-point
ip add 192.168.13.1 255.255.255.252
frame-relay interface-dlci 103
exit
interface loop 0
ip add 1.1.1.1 255.255.255.255
exit
router ospf 1
network 0.0.0.0 255.255.255.255 area 0
================
R2
==
Conf t
int ser 1/0
encapsulation frame-relay
no shut
exit
int ser 1/0.201 point-to-point
ip add 192.168.12.2 255.255.255.252
frame-relay interface-dlci 201
exit
interface loop 0
ip add 2.2.2.2 255.255.255.255
exit
router ospf 1
network 0.0.0.0 255.255.255.255 area 0

=========================
R3
==
Conf t
int ser 1/0
encapsulation frame-relay
no shut
exit
int ser 1/0.301 point-to-point
ip add 192.168.13.2 255.255.255.252
frame-relay interface-dlci 301
exit
interface loop 0
ip add 3.3.3.3 255.255.255.255
exit
router ospf 1
network 0.0.0.0 255.255.255.255 area 0

============================================
Testing with show commands and ping