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.Using you terminal communications package (such as minicom or seyon), set up themodem initialization required for PPP and dial into the PPP server you want to connect towith a PPP session.(Note: at this stage we are NOT trying to make a PPP connection just establishingthat we have the right phone number and also to find out exactly what the server sends tous 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 server gives to let you know it is timeto enter your user name and password (and any other commands needed to establish thePPP connection).If your server uses PAP, you should not see a login prompt, but should instead see the(text representation) of the link control protocol (which looks like garbage) starting on yourscreen.A few words of warning:some servers are quite intelligent: you can log in using text based username/passwords OR using PAP.So if your ISP or corporate site uses PAP but you donot see the garbage start up immediately, this may not mean you have done some-thing wrong.some servers require you to enter some text initially and then start a standard PAPsequence.Some PPP servers are passive that is they simply sit there sending nothing untilthe client that is dialing in sends them a valid lcp packet.If the PPP server you areconnecting to operates in passive mode, you will never see the garbage!Some servers do not start PPP until you press ENTER so it is worth trying this ifyou correctly log in and do not see the garbage! Dial-up Networking with PPP 273It is worth dialing in at least twice some servers change their prompts (e.g.with thetime!) every time you log in.The two critical prompts your Linux box needs to be able toidentify 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 you have to issue a command to start PPP on the server, you will also need to find outthe prompt the server gives you once you are logged in to tell you that you can now enterthe command to start PPP.If your server automatically starts PPP, once you have logged in, you will start to seegarbage on your screen this is the PPP server sending your machine information to startup and configure the PPP connection.This should look something like this :y}#.!}!}!} }8}!}}U}"}\&} } } } }}\&.} }"}(}"}.ÜÜy}On some systems PPP must be explicitly started on the server.This is usually be-cause 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.If you do not see this immediately after connecting (and logging in and starting the PPPserver if required), press Enter to see if this starts the PPP server.At this point, you can hang up your modem (usually, type +++ quickly and then issuethe ATH0 command once your modem responds with OK).If you can t get your modem to work, read your modem manual, the man pages for yourcommunications software and the Serial HOWTO.Once you have this sorted out, carry onas above.Using Internet servers with dynamic IP numbers.If you are using dynamic IPnumbers (and many service providers will only give you a dynamic IP number unless youpay significantly more for your connection), then you have to recognise the limitations thisimposes.First of all, outbound service requests will work just fine.That is, you can send emailusing sendmail (provided you have correctly set up sendmail), ftp files from remote sites,finger users on other machines, browse the web etc.In particular, you can answer email that you have brought down to your machine whilstyou are off line.Mail will simply sit in your mail queue until you dial back into your ISP. 274 Advanced FeaturesHowever, your machine is not connected to the Internet 24 hours a day, nor does it havethe same IP number every time it is connected.So it is impossible for you to receive emaildirected to your machine, and very difficult to set up a web or ftp server that your friendscan access! As far as the Internet is concerned your machine does not exist as a unique,permanently contactable machine as it does not have a unique IP number (remember othermachines will be using the IP number when they are allocated it on dial in).If you set up a WWW (or any other server), it is totally unknown by any user on theInternet UNLESS they know that your machine is connected AND its actual (current) IPnumber.There are a number of ways they can get this info, ranging from you ringing them,sending them email to tell them or cunning use of .plan files on a shell account at yourservice provider (assuming that your provider allows shell and finger access).For most users, this is not a problem all that most people want is to send and receiveemail (using your account on your service provider) and make outbound connections toWWW, ftp and other servers on the Internet.If you must have inbound connections to yourserver, you should really get a static IP number.PPP connection files.You now need to be logged in as root to create the directoriesand edit the files needed to set up PPP.PPP uses a number of files to connect and set up aPPP connection.These differ in name and location between PPP 2.1.2 and 2.2.For PPP 2.1.2 the files are:/usr/sbin/pppd # the PPP binary/usr/sbin/ppp-on # the dialer/connection script/usr/sbin/ppp-off # the disconnection script/etc/ppp/options # the options pppd uses for all connections/etc/ppp/options.ttyXX # the options specific to a connection on this portFor PPP 2
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