Take a divide-and-conquer layered approach to supporting the WAN. Determine whether the trouble is with you or the service provider. After verifying that interfaces and controllers are functioning properly, you can move on to Layer 3 and above. Extended ping and traceroute are wonderful tools to assist you with both connectivity and performance issues. Service time stamps are invaluable for understanding debug and log output. Clearing interface counters and statistics are important to start monitoring the data-link activity for a certain time period.

This chapter covered HDLC, PPP, and ISDN WAN technologies. PPP has several advantages over HDLC but a little more troubleshooting to go with it. Authentication is the key target. In supporting ...

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