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Frame Relay Switch

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One of the major topics on your CCNA and CCNP exams is Frame Relay. Additionally, Frame Relay is one of the most popular WAN technologies in today’s networks.

Getting hands-on experience with Frame Relay in Cisco networks isn’t just a good idea, it’s a necessity. Let’s face it, your employer is going to get a little touchy if you start experimenting with your network’s Frame Relay setup.

To practice all your important Frame Relay commands for your exams, you need a working Frame Relay cloud in your home lab. A production network’s Frame cloud consists of a lot of Frame switches, but if you choose wisely, a single Cisco router can act as your home lab’s entire Frame cloud!

Before we look at the configuration of such a router (hereafter referred to as a “frame relay switch”), let’s look at the physical requirements.

The more serial ports you have, the better. You should get a router with at least four serial ports. For frame switching purposes, it doesn’t matter if the ports are synchronous or asynchronous – you just need the ports.

You will also need some DTE/DCE cables. The DCE end of the cables will be connected to the frame switch.

A great configuration for a CCNA practice lab is three routers that serve as “production” routers, and a 4th router as a frame relay switch. (You’ll want an access server as well, but that’s another article.)

What I use in my student and customer pods is a setup where R1 is connected to the frame switch’s S1 port, R2 is connected to S2 on the frame switch, and R3 is connected to the frame switch’s S3 port.
Now comes the tricky part – the configuration. A frame relay switch’s config can be hard to find, so here’s a copy of mine. Pay particular attention to the config on ports s1, s2, and s3.

version 12.0
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname FRAME_SWITCH
!
!
ip subnet-zero
no ip domain-lookup
frame-relay switching
!
!
!
interface Ethernet0
no ip address
no ip directed-broadcast
shutdown
!
interface Serial0
ip address 10.1.1.2 255.255.255.0
clockrate 56000
!
interface Serial1
no ip address
no ip directed-broadcast
encapsulation frame-relay
logging event subif-link-status
logging event dlci-status-change
clockrate 56000
no frame-relay inverse-arp
frame-relay intf-type dce
frame-relay route 122 interface Serial2 221
frame-relay route 123 interface Serial3 321
!
interface Serial2
no ip address
no ip directed-broadcast
encapsulation frame-relay
logging event subif-link-status
logging event dlci-status-change
clockrate 56000
no frame-relay inverse-arp
frame-relay intf-type dce
frame-relay route 221 interface Serial1 122
!
interface Serial3
no ip address
no ip directed-broadcast
encapsulation frame-relay
logging event subif-link-status
logging event dlci-status-change
clockrate 56000
no frame-relay inverse-arp
frame-relay intf-type dce
frame-relay route 321 interface Serial1 123
!
interface BRI0
ip address 150.1.1.1 255.255.255.252
no ip directed-broadcast
encapsulation ppp
dialer map ip 150.1.1.2 name R2 broadcast 2335552221
dialer-group 1
!
ip classless
!
dialer-list 1 protocol ip permit
!
line con 0
exec-timeout 0 0
logging synchronous
transport input none
line aux 0
line vty 0 4
login
!
end


The key command in the global configuration is frame-relay switching. You must have this configured before you can configure the interfaces.

The interfaces will be configured with the frame route command. Let’s take a look at what each value means in the command frame-relay route 122 interface Serial2 221.

frame-relay route - the command
122 - the incoming DLCI on this interface
interface serial2 - the interface the data will be sent out
221 - the outgoing DLCI

This command on S1 means that anything that comes in on this port on DLCI 122 will be sent out interface serial2 on DLCI 221.

It’s a good idea to hard-code the interfaces to act as DCEs with the frame intf-type dce command. Since these interfaces are acting as DCEs, the clockrate command is needed for the line protocol to come up.
Once you’ve configured your frame switch as shown and have configured the frame map statements on the “production” routers, you can test the frame switch configuration. On the frame switch, run the command show frame route .

FRAME_SWITCH#show frame route
Input Intf Input Dlci Output Intf Output Dlci Status
Serial1 122 Serial2 221 active
Serial1 123 Serial3 321 active
Serial2 221 Serial1 122 active
Serial3 321 Serial1 123 active

You should see “active” for all the interfaces. If you see “deleted”, make sure your frame switch interfaces are open if they are, check the router configs.

Keep in mind that you can still configure routing protocols to run on ports that you’re not using for frame switching. The router we used here had an ethernet port and BRI port, and the BRI port has been configured as part of the production network. Running frame switching does not disable IP routing.

Purchasing and configuring your own frame relay switch is an invaluable part of your Cisco education. By practicing your frame commands and configuring frame connections over your own frame relay cloud, you’re polishing your Cisco skills and gaining knowledge that cannot be duplicated by simulator programs.

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (www.thebryantadvantage.com), home of FREE CCNA and CCNP tutorials and daily exam questions, as well as The Ultimate CCNA and CCNP Study Packages.

For a FREE copy of his latest e-books, “How To Pass The CCNA” or “How To Pass The CCNP”, and for free daily exam question, visit the website and download your copies!

Frame Relay Switch
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About Chris Bryant
Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (www.thebryantadvantage.com), home of FREE CCNA and CCNP tutorials and daily exam questions, as well as The Ultimate CCNA and CCNP Study Packages.

For a FREE copy of his latest e-books, "How To Pass The CCNA" or "How To Pass The CCNP", and for free daily exam question, visit the website and download your copies! WebProNews Writer
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