System Administration Guide: Network Services

General Communications Problems That Affect PPP

The following table describes symptoms that are related to log output from the procedure, How to Diagnose and Fix Communications Problems.

Table 21–3 General Communications Problems That Affect PPP




too many Configure-Requests

One peer cannot hear the other peer. 

Check for the following problems: 

  • The machine or modem might have faulty cabling.

  • The modem configuration might have incorrect bit settings. Or, the configuration might have broken flow control.

  • The chat script might have failed. In this situation, see Table 21–5.

The pppd debug output shows that LCP starts, but higher-level protocols fail or show CRC errors.

The asynchronous control character map (ACCM) is incorrectly set. 

Use the default-async option to set the ACCM to the standard default of FFFFFFFF. First, try to use default-async as an option to pppd on the command line. If the problem clears, then add default-async to /etc/ppp/options or to /etc/ppp/peers/peer-name after the call option.

The pppd debug output shows that IPCP starts but terminates immediately.

IP addresses might be incorrectly configured. 

  1. Check the chat script to verify whether the script has incorrect IP addresses.

  2. If the chat script is correct, request debug logs for the peer, and check IP addresses in the peer logs.

The link exhibits very poor performance. 

The modem might be incorrectly configured, with flow-control configuration errors, modem setup errors, and incorrectly configured DTE rates. 

Check the modem configuration. Adjust the configuration if necessary.