Serial Config 1

By Chris September 8, 2015 09:35

Take two routers in a lab, both with serial interfaces, and connect them with a back-to-back serial cable. Do you remember the details of how to configure both routers so that both routers can ping each other? Today’s lab provides that bit of practice, with a few other odds and ends.


Configure a serial link to the point where routers R1 and R2 can ping each other’s serial IP addresses. The specific rules for this lab are:

  • Use HDLC as the data link protocol
  • Assume the routers exist in a lab, and that the link is created with a back-to-back serial cable, with the DCE end in router R1
  • Set the speed of the link to 512 Kbps
  • Make sure both routers’ bandwidth setting is equal to the actual speed of the link.
  • Configure the serial IP addresses/masks as documented in the figure
  • Use no extra configuration commands beyond what is needed to meet these requirements

Figure 1: Two Routers with IP Subnets

Initial Configuration

There is no non-default configuration in these routers at all, other than possibly the hostname command.


Answer on Paper, or Maybe Test in Lab

Next, write your answer on paper. Or if you have some real gear, or other tools, configure the lab with those tools.

To test your solution if you happen to try it with real gear, all you need to do is cable the back-to-back cable and configure both ends. If both serial links remain in an up/up state, and you can ping the other router’s serial interface IP address. Note that with later IOS versions, the ping will work even without a few of the commands requested in this lab. You can check some parts of the lab with the show controllers and show interfaces commands.

A: A Port Security Question
Answers: Serial Config 1
By Chris September 8, 2015 09:35
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1 Comment

  1. Mike September 9, 20:12

    Dusting off some serial config knowledge. 😉
    Thanks Wendell!

    R1 (config)#int s0/0
    R1 (config-if)#ip addr
    R1 (config-if)#clock rate 512000
    ! R1 is the DCE, thus setting the clock (in bits) for this serial link
    R1 (config-if)#bandwidth 512
    R1 (config-if)#no shut
    ! default serial encapsulation is HDLC, no modification necessary


    R2 (config)#int s0/0
    R2 (config-if)#ip addr
    R2 (config-if)#bandwidth 512
    R2 (config-if)#no shut
    ! default serial encapsulation is HDLC, no modification necessary

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