Troubleshooting PPP

If you experience Point-to-Point Protocol (PPP) connection problems, you can use the checklist to gather error information. This checklist can help you identify error symptoms and resolve PPP connection problems.

Required supporting material:
- Remote host type, operating system, and level
- IBM® i operating system level
- All output files that are saved in an output queue with the same name as the profile
- Job logs for QTPPPCTL and QTPPPL2TP (if an L2TP profile)
- The connection script that is used in your environment
- Status of connection profile before and after the connection fails
Recommended supporting material:
- Line description
- Connection profile
  Option 6 from WRKTCPPTP prints the profile settings.
- Modem type and model
- Modem command strings
- Communications trace
  It is recommended that the DMPCMNTRC command is used to dump the communications trace to an IFS file with *PCAP format. *PCAP is a Packet Capture (PCAP) format, used by network protocol analyzers. For example:
```
DMPCMNTRC CFGOBJ(QPPPCMN06) CFGTYPE(*LIN) TOSTMF('/home/cmntrc.pcap') FORMAT(*PCAP)
```

To identify the problems and find out the solutions, see the checklist in the following table.

Table 1. PPP problems from ITSO Redbook
Problem	Solution
Modem hardware configuration Wrong configuration of dip-switches and other hardware settings	Make sure that the modem is configured for the correct framing type. This can be either Asynchronous or Synchronous. Refer to the modem manual for more information.
Modem AT commands The modem you are trying to use is not in the predefined list of modems in IBM Navigator for i.	Create a new modem.
PPP users and passwords You are getting user name and password errors when attempting a PPP connection.	Ensure that the user ID and password are entered using the same case. Ensure that the authentication protocol used by the peers is the same. Do not use PAP at one peer, while the other peer is configured as CHAP.
PPP lines for starting a connection profile Identified PPP lines are used by the same hardware resource.	Remember to vary off other lines using the same hardware resource.
PPP protocol Connection errors can occur due to misconfiguration of the PPP protocol.	Investigating the lower-levels of the PPP protocol might be necessary in some situations where the peers are unable to communicate with each other due to a configuration error. If the PPP log or the job log of the PPP job does not show any indication of the problem, you can investigate the problem by using the communications trace function.