Configuring the Point-to-Point Protocol (PPP)

Testing dedicated link connectivity

Verify host-to-host connectivity on the link as follows:

Turn on the PPP driver and PPP daemon logging. See ``Logging PPP information''.
Execute the following command:

ping remote_host_IP_address

If ping fails, it may fail with an error message. Below is one possible message:

   ping send: Network is unreachable

This error message indicates that the network address of the remote host is different from that of the local host. Make sure that the network portion of the remote host's IP address is correct. (See ``IP address'' for a discussion of the network portion of the IP address.) For machines on the same network, the network part of the IP addresses for the local host and the remote host should match. If the machines are not on the same network, you need to configure a gateway to route packets between the two networks.

If ping hangs with no response, make sure that the IP address used on the command line is correct. It should be the value assigned to the machine connected to the other end of the dedicated serial line. If the IP address appears to be correct, look in the logfile where the PPP driver and PPP daemon log information has been collected. By default, this file is /usr/adm/syslog. The following example logfile and the description below the example show the steps PPP uses to achieve host-to-host connectivity. You can view the logfile to see if these steps have been successful.

  1 Mar 14 09:31:54 127.0.0.1 pppd[318]: ppp_add_inf: 10.0.118.6 --> 10.0.118.9
  2 Mar 14 09:31:58 127.0.0.1 pppd[318]: Set static PPP on tty4d
  3 Mar 14 09:31:58 127.0.0.1 pppd[318]: ppp_add_conn
  4 Mar 14 09:31:59 127.0.0.1 pppd[318]: Assigned link id for dedicated link (10.0.
  5 118.6->10.0.118.9) is 84

line 1: the PPP daemon (shown as ``pppd'' in the logfile) builds the PPP network interface for the link
line 2: the PPP daemon links the tty specified in the PPP endpoint configuration under the PPP driver
line 4,5: the PPP daemon assigns a link ID (84) to the dedicated link

With knowledge of either the local or remote IP address for the PPP link you are troubleshooting, you can search on either in the /usr/adm/syslog file to see if the above activities completed successfully. Success is achieved if pppd assigned a link ID.

If ping is successful when using the IP address of the remote host, you may wish to test whether one can reach the remote host using the host names by which it should be reachable. See ``Using ping to test reachability using host names'' for the command, possible error message, and resolutions.

Next topic: Troubleshooting PPP negotiation
Previous topic: Verifying integrity of a dedicated serial line

© 2003 Caldera International, Inc. All rights reserved.
SCO OpenServer Release 5.0.7 -- 11 February 2003