Serial Point-to-Point Overview

HDLC Encapsulation

Cisco HDLC is the default encapsulation method used by Cisco devices on synchronous serial lines.

Use Cisco HDLC as a point-to-point protocol on leased lines between two Cisco devices. If connecting non-Cisco devices, use synchronous PPP.

If the default encapsulation method has been changed, use the encapsulation hdlc command in privileged EXEC mode to re-enable HDLC.

As shown in the figure, there are two steps to re-enable HDLC encapsulation:

Step 1. Enter the interface configuration mode of the serial interface.

Step 2. Enter the encapsulation hdlc command to specify the encapsulation protocol on the interface.