Cisco CCNA / CCNP Certification Training Tutorial:
Frame Relay Tips For Your Home Lab Network And Test Prep
By Chris Bryant, CCIE #12933
Frame Relay and Cisco certifications go hand-in-hand! During your CCNA training, you're introduced to Frame Relay basics such as the DLCI and Inverse ARP; when you're going after the CCNP certification, you have to take your knowledge to the next level to configure and troubleshoot Cisco routers with the right Frame Relay commands. In this exclusive certification training article, we'll take a look at some commands that CCNA and CCNP candidates sometimes trip on - but they're command that you will be more than ready for on exam day!
Certification Tip #1: Inverse ARP Starts Working As Soon As You Open The Interface
Inverse ARP sounds great, doesn't it? You just open a Cisco router's serial interface and inverse ARP will perform all the frame relay mappings! Well, maybe it will and maybe it will not; it's not the world's most dependable protocol. Inverse ARP is regularly turned off in today's networks with the no frame-relay inverse-arp command, but there's one thing you need to be careful about - this needs to be done before the serial interface is opened. If you enable Frame Relay and then open the interface, Inverse ARP will be running by default. To turn inverse ARP off:
R2(config)#interface serial0
R2(config-if)#encapsulation frame-relay
R2(config-if)#no frame-relay inverse-arp
Certification Tip #2: Frame Map Statements Have Local And Remote Information
A basic rule of Frame Relay is that Data Link Connection Identifiers are locally significant only. That's true, but the IP address you put in a Frame Relay map statement to go with that local DLCI is the remote router's IP address. For example, let's say you've been assigned DLCI 221 to reach a remote router at 172.12.123.1. Don't be fooled by any DLCI on the remote router, because that doesn't matter. Local DLCI, remote IP address!
R2(config)#interface serial0
R2(config-if)#frame map ip 172.12.123.1 221 broadcast
Certification Tip #3: The "show frame map" command indicates which mappings have been created dynamically and/or statically.
I'm not a fan of having both dynamic and static Frame Relay mappings on the same interface, but it can certainly be done. When you run the show frame map command, the word dynamic indicates a mapping performed by Inverse ARP. The word static indicates that this mapping was manually configured on the router.
R2#show frame map
Serial0 (up): ip 0.0.0.0 dlci 221(0xDD,0x34D0), dynamic,
broadcast, CISCO, status defined, active
Serial0 (up): ip 172.12.123.1 dlci 221(0xDD,0x34D0), static,
broadcast, CISCO, status defined, active
Certification Tip #4: To Configure A Cisco Router As A Frame Relay Switch, Use The "frame-relay switching" command.
For those of you considering a Cisco CCNA or CCNP training home lab, a frame relay switch is a tremendous addition. You can make just about any Cisco router into a frame switch; I recommend getting one with as many serial interfaces as you can, since it's those interfaces that you'll be using to connect to the other routers. To get started on this router configuration, just run the global command frame-relay switching.
R4#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R4(config)#frame-relay switching
The best part about configuring a Cisco router as a Frame Relay switch is that you can still use other ports on the router as routing ports. For example, you could use four serial ports on the router for Frame Relay switching and then run a routing protocol on any remaining ports, including other serial ports. To learn more about Frame Relay switches, visit my website's Home Lab Help section to learn more about Cisco training on routers and switches in your own home!
To your success,
Chris Bryant
CCIE #12933
chris@thebryantadvantage.com
|
