REMEMBER THE DEBUGGING TECHNIQUES YOU WILL LEARN IN THE CLASS. LEAR...

8. Remember the debugging techniques you will learn in the class. Learn how to prove to yourself that every configuration is correct by using the appropriate debug or show commands.

Skills Needed for the CCIE Lab

Although there are many direct skills you need to learn for the CCIE lab exam, there are some indirect skills as well. Some of the indirect skills you need to learn are how to configure a router to act as a frame-relay switch and how to configure a terminal server. You may want to know how to configure an ATM switch to practice with.

How to Configure a Router as a Frame Switch

One of the skills that you need to learn for the CCIE lab is how to configure a router as a frame-relay switch. It isn't so much that you need to be able to configure a router as a frame-relay switch for the lab itself (although if a given configuration is in IOS, it is still fair game). Rather, it is the fact that you need to be able to configure a router as a frame-relay switch to practice your own scenarios since you will want to study frame-relay heavily. The commands you need to configure a router as a frame switch are relatively simple. In this example, we are assuming that you have a router with at least four serial ports, although you could easily have more, e.g. a 2522 has 10 serial ports. Here is a step-by-step example:You need to use the global command frame-relay switching to enable frame-relay switching. This is the only global command you need. All the rest are interface commands.The next command you need to enter is an interface command to define the frame-relay interface type as a DCE. Remember that, in general, the DCE side of the circuit is on the telco side, and the DTE side is on the Customer Premises Equipment (CPE) side. The next command defines the routing between the DLCIs, so it is very important that you understand the syntax of the frame-relay route command. Here is a practical example:Frame-switch#config tFrame-switch(config)#frame-relay switchingFrame-switch(config)#interface s 0Frame-switch(config-if)#encapsulation frame-relay ietfFrame-switch(config-if)#frame-relay intf-type dceFrame-switch(config-if)#frame-relay route 102 interface serial1 201Frame-switch(config-if)#frame-relay lmi-type q933aNote that the encapsulation frame-relay command actually specifies which of the two frame-relay encapsulation types the circuit will use: cisco (the default), or ietf (the standard for connecting to other manufacturer's equipment). You can also set which of the three lmi-types you want to use here: cisco (the default), CCITT (q933a), or ANSI. Finally, look at the syntax of the frame-relay route command itself. This is where you set the DLCI for each interface. The example above is saying that all data from interface s 0 will use DLCI 102 to reach interface s 1 using DLCI 201. It should be obvious that interface s 1 needs a similar configuration. Here is what it looks like:Frame-switch(config)#interface s 1Frame-switch(config-if)#frame-relay route 201 interface serial0 102From your reading, you should be aware that significant differences exist between a fully meshed network and a partially meshed network. For frame-relay, a partial mesh presents many difficulties. It is imperative that you understand the differences between the two types of meshed networks.More detailed information about Frame Relay can be found in the CertificationZone Frame Relay Study Guide.

Fully Meshed Frame Switch

Figure 5. A Fully Meshed Frame-relay NetworkIn this simple example of a fully meshed network of three routers, notice how each interface has two frame-relay route statements associated with it. You should see that each frame-relay route statement has a complement under its paired interface.Frame-switch#show runBuilding configuration...Current configuration:!version 11.3hostname Frame-switchframe-relay switchinginterface Serial0no ip addressencapsulation frame-relayframe-relay intf-type dceframe-relay route 102 interface Serial1 201frame-relay route 103 interface Serial2 301interface Serial1clockrate 56000frame-relay route 201 interface Serial0 102frame-relay route 203 interface Serial2 302interface Serial2frame-relay route 301 interface Serial0 103frame-relay route 302 interface Serial1 203no ip classlessline con0line aux0line vty 0 4loginend

Partially Meshed Frame Switch

Figure 6. A Partially Meshed Frame SwitchIn our next example, R1 is serving as the hub router with R2 and R3 as the spokes. Notice how on the frame-switch the serial0 interface, connected to the hub, has two frame-relay route statements, but the other serial interfaces, connected to the spokes, only have a single statement each.By now you probably are wondering whether the best way to practice for the lab is to configure your frame-relay switch as a fully meshed switch or as a partially meshed switch. I personally prefer to configure the frame-switch as a fully meshed switch because this gives me the best flexibility. If I want to practice scenarios using a full mesh, I can. If I want to practice scenarios using a partial mesh, I can do that too by simply disabling inverse-arp on the routers in question for any DLCIs that I don't want to use. I suggest that you practice with both scenarios so that you are completely familiar with the limitations of partial mesh topologies compared to fully meshed topologies. Before we move on to configuring terminal servers, let's take a quick look at how to verify that the frame-relay switch is working correctly. All you need to do is use the show frame route command. You should then see a display that looks similar to this:Frame-switch#show frame routeInput Intf Input Dlci Output Intf Output Dlci StatusSerial0 102 Serial 1 201 activeSerial0 103 Serial 2 301 activeSerial1 201 Serial 0 102 activeSerial1 203 Serial2 302 activeSerial1 301 Serial0 103 activeSerial2 302 Serial1 203 activeAll PVCs should show active. If they do not show active then troubleshoot as follows: