Chapter 4. WAN Protocols and Technologies: Point-to-Point Protocol (PPP)

Lab 9: Configuring HDLC ”Part I

Practical Scenario

HDLC can have many uses in the field. One instance, as mentioned previously, is to always switch the encapsulation to HDLC when testing a CSU/DSU or an internal CSU/DSU with a loopback plug. HDLC is often used when connecting to a Cisco router administered by a third party. A third-party router is a router that is not part of your autonomous system or one that is not under your direct control. HDLC provides for a quick and easy configuration, minimizing the number of problems that can go wrong because of configuration errors.

Lab Exercise

In this exercise, you are a network engineer for ACME Finance. ACME Finance is about to have a new credit card authorization center and a Wisconsin branch join the network. The credit card center, cc_center, is running HDLC protocol on a 56-kbps link to your distribution router, acme_dist. The credit card center would like to improve performance on this link as soon as possible, by using payload compression. The Wisconsin branch router, wi_branch, has a T1 leased line into acme_dist router, but it is not configured. The WAN is the first circuit in each building, and there are no users; therefore, you won't be concerned with any LAN configurations.

Lab Objectives

• Configure the network as depicted in Figure 3-2.

  Figure 3-2. ACME Finance Network

  

• Use only the HDLC protocol on the serial links.

• Use payload compression on the 56-kbps link between the cc_center and acme_dist routers.

Equipment Needed

• Three Cisco routers. One must have two serial ports.

• Four serial cables, preferably two V.35 DTE male and two V.35 DCE female cables. Otherwise, you can use the correct speed of CSU/DSUs with a crossover cable between them. When using actual CSU/DSUs, the clock rate interface command is not needed. For more information on the various ways to connect routers in a back-to-back manner, review Chapter 1, "The Key Components for Modeling an Internetwork."

Physical Layout and Prestaging

• Connect the serial cables to the routers as shown in Figure 3-2.