Configuring a frame-relay switch and core router using 1 router

Contributed by Headhunter December 6, 2004  
Tagged: Cisco router

This recipe will show how to configure a Frame-Relay switch and a core router within one router creating a hub-and-spoke topology.

You can use this recipe on 2521/2522 and 2600 series routers, just remember to change the interface numbering when you use a 2600 with the async/sync module
The first step we do is enable Frame-Relay switching with the frame-relay switching global configuration command.
Now we configure the rest of the switch, to ease the configuration make sure all DCE cables are on this router.
Let’s assume 2 spokes and 1 hub in this topology.
To simulate the core router we connect a DCE cable in serial 0 and the DTE in serial 1.
Here is the configuration for the core/frame-relay switch:

interface serial0
encapsulation frame-relay
clockrate 64000
frame-relay intf-type dce
frame-relay route 220 interface serial2 120
frame-relay route 230 interface serial3 130
!
interface serial1
encapsulation frame-relay
!
interface serial1.220 point-to-point
ip address x.x.x.x y.y.y.y
frame-relay interface-dlci 220
!
interface serial1.230 point-to-point
ip address a.a.a.a b.b.b.b
frame-relay interface-dlci 230
!
interface serial2
encapsulation frame-relay
clockrate 64000
frame-relay intf-type dce
frame-relay route 120 interface serial0 220
!
interface serial3
encapsulation frame-relay
clockrate 64000
frame-relay intf-type dce
frame-relay route 130 interface serial0 230
!


The IP addresses on the subinterfaces are the ones you configure.

A spoke will have the following configuration

interface serial0
ip address x.x.x.x y.y.y.y
encapsulation frame-relay
frame-relay interface-dlci 120


When assigning IP addresses to the spokes just remember to put them in the same subnet as the sub-interfaces.

For more information about Frame-Relay Switching see the configuring Frame-Relay switching recipe.