Cisco Certified Network Associate (CCNA) Practice Exam

To configure HDLC on a serial interface, which command must be used?

1. encapsulation ppp

2. encapsulation hdlc

3. ip address

4. bandwidth calculation

The correct answer is: encapsulation hdlc

To configure HDLC (High-Level Data Link Control) on a serial interface, the command "encapsulation hdlc" is utilized. This command is essential because it explicitly sets the encapsulation method for the serial link to HDLC, a protocol used for framing packets in point-to-point networks. HDLC is a default encapsulation method on Cisco routers for serial links, meaning when you configure a serial interface, it typically uses HDLC unless specified otherwise. This command ensures that the router frames the data properly for transmission over the serial link, facilitating communication with the device on the other end that also needs to support HDLC. In contrast, the other commands listed are not relevant for configuring HDLC on a serial interface. For instance, "encapsulation ppp" is used to set up Point-to-Point Protocol (PPP) for encapsulation, which is different from HDLC. The command "ip address" is utilized for assigning an IP address to an interface, which is unrelated to the encapsulation type. Lastly, "bandwidth calculation" refers to evaluating the bandwidth but does not configure the encapsulation type of the serial interface. Thus, using "encapsulation hdlc" is the appropriate command to configure HDLC properly.