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TX packets:1288 errors:0 dropped:0 overruns:0 carrier:0

collisions:0

Memory:73038-73c04

Here, we can see that PPP is up, the local IP address is 207.25.97.248, and the remote server IP address is 207.25.97.154.

If you wish to be notified when the PPP connection is established (the ppp-on script returns immediately), add the following line to /etc/ppp/ip-up:

/usr/bin/wall "PPP is up!"

/etc/ppp/ip-up is executed when PPP establishes an IP connection, so you can use this script to trigger the wall command when the connection is complete.

Another simple shell script can be used to kill the PPP session. Edit the file /etc/ppp/ppp-off as follows:

#!/bin/sh

# A simple ppp-off script

kill `cat /var/run/ppp0.pid`

Running /etc/ppp/ppp-off now kills the PPP daemon and shuts down the modem connection.

Configuring DNS

By itself, use of pppd along with chat only establishes a PPP connection and assigns you an IP address; in order to use domain names, you need to configure the system to be aware of the domain nameserver provided by your ISP. You do this by editing /etc/resolv.conf. The manpage for resolver describes this file in detail. However, for most purposes it suffices to simply include lines of two forms: one that specifies the list of domains to search whenever a domain name is used, and another that specifies the address of a DNS server.

A sample /etc/resolv.conf file might look like this:

# Sample /etc/resolv.conf

search cs.nowhere.edu nowhere.edu

nameserver 207.25.97.8

nameserver 204.148.41.1

The first line indicates that every time a domain name is used (such as orange or papaya), it should be searched for in the list of specified domains. In this case, resolver software would first expand a name like papaya to papaya.cs.nowhere.edu and try to find a system by that name, then expand it to papaya.nowhere.edu if necessary and try again.

The lines beginning with nameserver specify the IP address of domain nameservers (which should be provided by your ISP) that your system contacts to resolve domain names. If you specify more than one nameserver line, the given DNS servers will be contacted in order, until one returns a match; in this way, one DNS server is treated as a primary and the others as backups.

Troubleshooting PPP configuration

The PPP configuration described here is meant to be very simple and will certainly not cover all cases; the best sources for additional information are the manpages for pppd and chat as well as the Linux PPP HOWTO and related documents.

Happily, both chat and pppd log messages on their progress, as well as any errors, using the standard syslog daemon facility. By editing /etc/syslog.conf, you can cause these messages to be captured to a file. To do this, add the following lines:

# Save messages from chat

local2.* /var/log/chat-log

# Save messages from pppd

daemon.* /var/log/pppd-log

This will cause messages from chat to be logged to /var/log/chat-log, and messages from pppd to be logged to /var/log/pppd-log.

Note that these log messages will contain private information, such as ISP usernames and passwords! It is important that you leave this logging enabled only while you are debugging your PPP configuration; after things are working, remove these two logfiles and remove the lines from /etc/syslog.conf.

chat will also log certain errors to /etc/ppp/connect-errors, which is not controlled through the syslog daemon. (It should be safe to leave this log in place, however.)

PAP and CHAP

Some ISPs may require you to use a special authentication protocol, such as PAP (Password Authentication Protocol) or CHAP (Challenge Handshake Authentication Protocol) . These protocols rely on some form of "shared secret" known to both the client and the server; in most cases, this is just your ISP account password.

If PAP or CHAP is required by your ISP, they are configured by adding information to the files /etc/ppp/pap-secrets and /etc/ppp/chap-secrets, respectively. Each file has four fields separated by spaces or tabs.