Lab 5. Configuring Back-to-Back Serial Connections

3 min readAug 8, 2022

CCNA 200–301

Lab Objective:

The objective of this lab exercise is to configure back-to-back Serial interfaces between two Cisco routers. By default, router Serial interfaces receive their clocking information from an external device such as a CSU/DSU.

Lab Purpose:

Back-to-back Serial interface configuration is a fundamental skill. Because routers typically receive clocking from an external device such as a CSU/DSU, it is imperative to understand how to bring up a back-to-back Serial connection between two routers to set up your home lab, for example. As a Cisco engineer, as well as in the Cisco CCNA exam, you will be expected to know how to configure back-to-back Serial connections.

Simulator

Cisco Packet Tracer

Lab Topology:

Please use the following topology to complete this lab exercise:

Task 1:

Configure hostnames on R1 and R2 as illustrated in the topology.

Task 2:

Enable Serial interfaces on R1 and R2. The Serial0/1/0 interface on R2 is identified as the DCE in the topology. Use the appropriate show command to verify that this interface is indeed the DCE.

Task 3:

Configure the DCE interface on R2 to provide clocking to R1. The clock speed should be 250 Kbps. Remember that 1 Kbps = 1000 bps. Verify that R1 receives clocking information from R2.

Task 4:

Configure IP addressing on R1 and R2 Serial0/1/0 interfaces as illustrated in the topology.

Task 5:

Verify your interface status and ping between R1 and R2 to validate connectivity.

Task 1:

For reference information on configuring hostnames, please refer to earlier labs.

Task 2:

R1(config)#interface serial0/1/0
R1(config-if)#no shut
R1(config-if)#end

R2(config)#interface serial0/1/0
R2(config-if)#no shut
R2(config-if)#end

NOTE: The show controllers command will tell you whether the interface is the DCE side (which provides the clocking) or the DTE side (which receives the clocking) on a particular router interface.