HDLC and PPP configuration is straightforward. You only need to be sure that the same WAN data-link
protocol is configured on each end of the serial link because each WAN data-link protocol uses a different
frame format. The command used to configure which protocol to use is: encapsulation {hdlc | ppp}.
The compress [predictor | stac | mppc [ignore-pfc]] command can be used to configure compression. The
predictor, stac or mppc options specify which compression algorithm must be used. These are predictor
for predictor, Stacker (LZS) for stac and MPPC for mppc. The ignore-pfc option specifies that the
protocol field compression flag negotiated through LCP will be ignored.
There are also a few show commands that can be used to troubleshoot HDLC and PPP. These are:
• show interfaces[type number] , which lists statistics and details of interface configuration, including
the encapsulation type;
• show compress, which lists compression ratios; and
• show processes[cpu], which lists processor and task utilization. This is useful for monitoring the
impact of compression.