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.For complete information on setting up PPP under Linux, we encourage you to readthe Linux PPP HOWTO, available via anonymous FTP fromsunsite.unc.edu.ThePPP HOWTO is a complete guide to configuring PPP, including modem, ISDN and null-modem cables, under Linux.Much of the information in this section was gleaned fromthis document.The Linux Network Administrator s Guide, from the Linux DocumentationProject, is also available.See Appendix A for more information on these documents.6.2.1 What you need to get started.We assume that your kernel has been configured and compiled with TCP/IP supportenabled.See Section 4.9 for information on compiling your kernel.To enable networking,you must answer yes to the appropriate questions during themake configstep, andrebuild the kernel.We also assume that ppp has been compiled and installed on your systemas well.We assume that you are using a Linux 1.2.x kernel with the PPP 2.1.2 software orLinux 1.3.X/2.x and PPP 2.2.At the time of writing, the latest official version of PPPavailable for Linux is ppp-2.2f.Please see the kerneld mini-HOWTO if you plan to usemodules to load ppp into your kernel.It is highly recommended that you use a version ofthe Linux kernel and the appropriate PPP version that are known to be stable together.You should also readthe documentation that comes with the PPP package;the pppd and chat man pages; (use man chat and man pppd to explore these)the Linux Network Administration Guide (NAG);the Net-2/3 HOWTO;Linux kernel documentation installed in /usr/src/linux/Documentation when you in-stall the Linux source code; Dial-up Networking with PPP 267The modem setup information page see Modem Setup Information(http://www.in.net/info/modems/index.html)The excellent Unix/Linux books published by O Reilly and Associates.See(O Reilly and Associates On-Line catalog (http://www.ora.com/).If you arenew to Unix/Linux, run (don t walk) to your nearest computer book shop and investin a number of these immediately!The PPP-FAQ maintained by Al Longyear, avail-able from (ftp://sunsite.unc.edu/pub/Linux/docs/faqs; see Ap-pendix B).This contains a great deal of useful information in question/answer formatthat is very useful when working out why PPP is not working (properly).6.2.2 An overview of the steps involved.There are several steps to setting up your system to use PPP.We recommend that youread through all of these steps thoroughly before attempting to actually bring up a PPPconnection.Each of these steps will be discussed in detail later.1.Make sure that TCP/IP support is compiled into your kernel.2.Make sure that PPP support is compiled into your kernel either statically or as aloadable module.3.Make sure that PPP software is compiled and installed on your systems.4.Make sure that you have a modem configured and installed/attached to your computerand that you know which serial port the modem is assigned to.5.Make sure you have the following information from your PPP dialup server provider(usually an ISP)The phone number you will dial to connect to the remote PPP dialup serviceprovider.Whether or not you are using dynamic or static IP assignment.If the latter, youwill need to know that static IP number.The IP addresss of the DNS (Domain Name Service) server that you will beusing to resolve host names when connected 268 Advanced FeaturesMake sure that the kernel has TCP/IP support.Linux PPP operations come in twoparts: 1) the PPP daemon and kernel support for PPP.Most distributions seem to providePPP kernel support in their default installation kernels, but others do not.You should makesure that TCP/IP is compiled into your kernel.You can do this by issuing the followingcommand:grep -i TCP/IP /var/adm/messagesIf you get a line similar toJun 8 09:52:08 gemini kernel: Swansea University Computer Society TCP/IP for NET3.019then you have TCP/IP support compiled in.You can also look for the above informationon the console while Linux is booting.On many fast machines, this scrolls by too quickly.You can use Shift - PageUp to scroll the screen up and see this.Make sure that the kernel has PPP support.If at boot your kernel reports messageslikePPP Dynamic channel allocation code copyright 1995Caldera, Inc.PPP line discipline registered.then your kernel has PPP support.You can also issue the command# grep -i PPP /var/adm/messagesIf you get a line similar toJun 8 09:52:08 gemini kernel: PPP: version 0.2.7 (4 channels) NEW_TTY_DRIVERS O PTIMIZE_FLAGSthat means PPP support is present.Make sure that you have a modem configured.You should make sure that yourmodem is correctly set up and that you know which serial port it is connected to.DOS com1: = Linux /dev/cua0 (and /dev/ttyS0)DOS com2: = Linux /dev/cua1 (and /dev/ttyS1),et cetera Dial-up Networking with PPP 269Historically, Linux used cuax devices for dial out and ttySx devices for dial in.Thekernel code that required this was changed in kernel version 2.x and you should now usettySx for both dial in and dial out.The cuax device names may well disappear in futurekernel versions.If you are using a high speed (external) modem (14,400 Baud or above), your serial portneeds to be capable of handling the throughput that such a modem is capable of producing,particularly when the modems are compressing the data.This requires your serial port to use a modern UART (Universal Asynchronous Re-ceiver Transmitter) such as a 16550A.If you are using an old machine (or old serial card),it is quite possible that your serial port has only an 8250 UART, which will cause youconsiderable problems when used with a high speed modem.Use the command# setserial -a /dev/ttySxto get Linux to report to you the type of UART you have.If you do not have a 16550Atype UART, invest in a new serial card (available for under $50)
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