Verifying or Troubleshooting a Serial LinkPPP Encapsulation

Verifying or Troubleshooting a Serial Link/PPP Encapsulation

Router#show interfaces serial x	Lists info for serial interface x
Router#show controllers serial x	Tells you what type of cable (DCE/DTE) is plugged into your interface and whether a clock rate has been set
Router#debug serial interface	Displays whether serial keepalive counters are incrementing
Router#debug ppp	Displays any traffic related to PPP
Router#debug ppp packet	Displays PPP packets that are being sent and received
Router#debug ppp negotiation	Displays PPP packets related to the negotiation of the PPP link
Router#debug ppp error	Displays PPP error packets
Router#debug ppp authentication	Displays PPP packets related to the authentication of the PPP link
Router#debug ppp compression	Displays PPP packets related to the compression of packets across the link

Tip:

With frequent lab use, serial cable pins often get bent, which may prevent the router from seeing the cable. The output from the command show controllers interface serial x will show no cable even though a cable is physically present.