7. Getting the Information you need about the PPP service

Before you can establish a PPP connection with a server, you need to obtain the following information (from the sysadmin/user support people of the PPP server):-

• The telephone number(s) to dial for the service (if you are behind a PABX, you also need the PABX number that gives you an outside dial tone - this is frequently digit zero)
• Does the server use DYNAMIC or STATIC IP numbers? If the server uses STATIC IP numbers, then you need to know what IP number to use for your end of the PPP connection.
  Most Internet Service Providers use DYNAMIC IP numbers. As mentioned above, this has some implications in terms of the services you can use!
• If you are using static IP numbers, ask for the network mask as well.
• What are the IP numbers of the server's Domain Name Servers? (There should be at least two.)
• Does the server require the use of PAP/CHAP?
• Does the server automatically start PPP or do you need to issue any commands to start PPP on the server once you are logged in? If you must issue a command to start PPP, what is it?

Carefully note down this information - you are going to use it!

7.1 Testing your Modem Connection

You should make sure that your modem is correctly set up and that you know which serial port it is connected to.

Remember

• DOS com1: = Linux /dev/cua0 (and /dev/ttyS0)
• DOS com2: = Linux /dev/cua1 (and /dev/ttyS1)
  et cetera

Using you terminal communications package (such as minicom), dial into the PPP server you want to connect to with a PPP session. (Note: at this stage we are NOT trying to make a PPP connection - just establish that we have the right phone number and also to find out exactly what the server sends to us in order to get logged in and start PPP).

During this process, either capture (log to a file) the entire login process or carefully (very carefully) write down exactly what prompts the remote server gives to let you know it is time to enter your user name and password (and any other commands needed to establish the connection).

It is worth dialling in at least twice - some servers change their prompts (eg with the time!) every time you log in. The two critical prompts your Linux box needs to be able to identify every time you dial in are:-

• the prompt that requests you to enter your user name;
• the prompt that requests you to enter your password;

If your server automatically starts PPP, once you have logged in, you will start to see garbage on your screen - this is the PPP server sending your machine information to start up the PPP connection.

This should look something like this :-

~y}#.!}!}!} }8}!}$}%U}"}&} } } } }%}& ...}'}"}(}"} .~~y}

(and it just keeps on coming!)

At this point, you can hang up your modem (usually, type +++ quickly and then issue the ATHO command once your modem responds with OK).

On some systems PPP must be explicitly started on the server. This is usually because the server has been set up to allow PPP logins and shell logins using the same username/password pair. If this is the case, issue this command once you have logged in. Again, you will see the garbage as the server end of the PPP connection starts up - so you can now hang up.

If you do NOT see the garbage on your screen when the server starts up PPP, it is quite likely (though not certain) that you have done something wrong.

Notwithstanding this, some PPP servers are set up to be passive - they send nothing until the client (your computer) starts the PPP process.

However, the majority of servers are active and you should see the garbage.

If you can't get your modem to work, read your modem manual, the man pages for your communications software and the Serial-HOWTO. Once you have this sorted out, carry on as above.