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Testing and Automating PPP
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Possible problems

The PPP setup returns the error "Could not determine remote IP address".
This means that your ISP has a damaged implementation of PPP, which does not know (or refuses to report) who it is. So you need to assign your ISP an IP number. Put the lines


into the /etc/ppp/options file. These lines assign your ISP the IP number (a "reserved" IP number) because they refuse to tell you theirs, and also tells pppd to accept their version if at this point they wake up and finally send you an IP address.

If this happens, you might want to notify your ISP that they should know their own IP number.

Ping works -- the ping tests above all worked -- but telnet or surfing does not seem to work.
Again your ISP seems to have a defective version of PPP. Try putting the line


into /etc/ppp/options. This disables compression of the headers on the packets which often causes problems.

Miscellaneous error messages

There are a few error messages which crop up with the newer versions of PPP and the newer (2.2.x) kernels.

On the 2.3.9 and 2.3.10 versions of pppd, the message modprobe: can't locate module char-major-108 is displayed in the log file. Ignore this. These versions of pppd use some new features of the PPP kernel drivers in the development kernels on Linux if they are available. This message says PPP cannot find these features. This is fine as these versions of PPP also work perfectly well with the older (2.0.x and 2.2.x) kernels.

You may see a series of lines like

modprobe: Can't locate ppp_compress-21

or 24 or 26. Put the following three lines into /etc/conf.modules (/etc/modules.conf on the 2.4.x series of kernels)

alias ppp-compress-21   bsd_comp
alias ppp-compress-24   ppp_deflate # From original RFC draft
alias ppp-compress-26   ppp_deflate # Final standard per ppp-2.3.4

Again these error messages cause no harm -- except in the unlikely event that the remote side supports these compression modes, you will not be able to use these compressions. (Modems today do compression themselves, so the advantages of software compression are often minimal).

Automation and clean up

Typing the above command line every time you want to connect can get tiring and be prone to errors. It also suffers from the problem that it must be run by "root," not an ordinary user, and is also insecure in that details like passwords are left lying around on the command line for anyone who can run the command ps to see. Thus, we want to enable the programs to be run by any user and make them easy to use. We also want to make sure that it is at least somewhat secure.

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