Troubleshooting PPP links

Link initiation

In this example, the command ppptalk attach Annex was used to initiate an outgoing PPP connection to the remote system Annex over the modem port /dev/term/00m.

1   Link link_0 : Dialing remote system 'Annex', telno '', dev '/dev/term/00m'
2   Link link_0 : Hardware flow control selected
3   Link link_0 : Links index 27
4   Link link_0 : Phase was DEAD, Phase Now ESTABLISH
5   Bundle Annex: Adding link link_0 to the bundle

If the connection was incoming, you would see messages such as the following:

1   Incoming call: dev '/dev/term/00m', uid 'foo', speed '19200'
2   Link link_0 : Incoming call
3   Link link_0 : Hardware flow control selected
4   Link link_0 : Phase was DEAD, Phase Now ESTABLISH
5   Bundle test : Adding link link_0 to the bundle

In this case, the incoming user logged in as foo and the PPP shell (pppsh) was initiated because the Callservices(4bnu) file defined this as the call service for port /dev/term/00m:

   acu Any /dev/term/00m /bin/pppsh

Outgoing link is brought up unexpectedly

If an outgoing link is often brought up unexpectedly, use the PPP Manager to turn on debugging in the bundle, and in the network protocol (IPCP) definition that the bundle references:

ppptalk protocol ipcp_tag debug=1
ppptalk bundle bundle_tag debug=high

NOTE: To discover the name of the IPCP tag (ipcp_tag), enter the following command:

ppptalk list bundle bundle_tag | grep protocols

This level of debugging will log all IP packets and will perform decoding of TCP/IP headers. You will now be able to examine the type of IP traffic that is bringing up the link. Common causes are requests for DNS name service (to port/protocols: 53/tcp and 53/udp) and for SMTP mail transfers (to port/protocol: 25/tcp). If necessary, invoke the Packet Filter Manager and configure a bringup filter which will stop packets requesting these services from bringing up the link. Alternatively, it may sometimes be possible to reconfigure requests for these services so that they send packets to local machines rather than over the PPP interface.