Configuring a Frame-Relay Switch and Core Router Using One Router

Posted December 6, 2004 by Headhunter in Cisco router

Frame-Relay is a fundamental concept of networking. This tech-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 tutorial 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 is to enable Frame-Relay switching with the frame-relay switching global configuration command.
Then, we configure the rest of the switch. To ease the configuration, make sure all DCE cables are on this router.

We will assume two spokes and one 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 tech-recipe.

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