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Path: senator-bedfellow.mit.edu!bloom-beacon.mit.edu!gatech!concert!samba.oit.unc.edu!sunSITE!mdw From: terryd@extro.ucc.su.oz.au (Terry Dawson) Newsgroups: comp.os.linux.announce,comp.os.linux.help,comp.os.linux.admin,news.answers,comp.answers Subject: Linux NET-2 HOWTO Followup-To: poster Date: 15 Dec 1993 22:08:56 GMT Organization: The University of North Carolina at Chapel Hill Lines: 1536 Approved: linux-announce@tc.cornell.edu (Matt Welsh) Message-ID: <2eo1to$651@samba.oit.unc.edu> NNTP-Posting-Host: calypso.oit.unc.edu Summary: HOWTO on configuration of TCP/IP networking and SLIP under Linux. Keywords: Linux, Networking, TCP/IP, NET-2, SLIP Originator: mdw@sunSITE Xref: senator-bedfellow.mit.edu comp.os.linux.announce:1569 comp.os.linux.help:13115 comp.os.linux.admin:2502 news.answers:15868 comp.answers:3044 Archive-name: Linux/HOWTO/NET-2-HOWTO Last-modified: 05 Dec 93 This is the Linux NET-2 HOWTO (previously known as the NET-2-FAQ). This document explains how to configure TCP/IP and SLIP with the new ``NET-2'' networking code in Linux kernels 0.99.pl13 and above. Please mail me if you have questions or comments. --terryd This is the Linux NET-2 HOWTO v1.9, 05 December 1993 By Terry Dawson <terryd@extro.ucc.su.oz.au> and Matt Welsh <mdw@sunsite.unc.edu> CHANGES from previous version: correction to broadcast address calculation, thanks Andr'as Salamon tcp/ip tutorials added thanks to Gilbert Callaghan These annotations at the suggestion of Andy Burgess Shadow password section updated - thanks Rick Sladkey added Slip Server section - thanks Fred added /etc/net/diphosts section - thanks Fred enhanced the netmask description a little Revamped for 0.99.14 Added Index *** FTP site maintainers: This document should be stored in the docs/HOWTO *** directory on your Linux archive as ``NET-2-HOWTO''. You may also wish *** to link this file to ``NET-2-FAQ'' (its previous name). This document *** also supercedes the old Linux NET-FAQ. "Real Programmers don't write documentation." --Ancient Proverb INDEX for this version To search for a particular section, search for '^N.S' where N is the section, and S is the Subsection. 0. Introduction 0.1 Disclaimer 0.2 Questions already? 0.3 Related documentation 0.4 New versions of this document 0.5 Feedback 1. NET-2 Supported Functionality 1.1 Supported Ethernet cards 2. Getting the NET-2 Software 2.1 Unpacking the software 2.2 Putting things in the right place 2.3 Creating the device interfaces 3. Building the Kernel 3.1 Configuring the NET-2 kernel code 3.2 Building the kernel 4. Configuring NET-2 TCP/IP 4.1 Before you begin 4.2 /etc/rc.d/rc.inet1 and /etc/rc.d/rc.inet2 4.2.1 Editing rc.inet1 4.2.2 Editing rc.inet2 4.2.2.1 "To named or not to named... that is the question." 4.3 /etc/hosts 4.3.1 Important note 4.4 /etc/networks 4.5 /etc/host.conf 4.6 /etc/resolv.conf 4.7 /etc/HOSTNAME 4.8 /etc/rc.local 4.9 Other files 5. Configuring SLIP 5.1 Static SLIP server connections 5.2 Dynamic SLIP server connections 5.3 Using DIP 5.4 Configuring your Linux Machine as a SLIP Server 5.5 /etc/net/diphosts 5.6 Configuring Plip interfaces 5.6.1 PLIP Cabling Diagram 6. Are You Stuck? 7. Common Problems and Solutions 8. Known bugs 9. Miscellaneous ------------------------------------------------------------------------------ 0. Introduction This is the NET-2 HOWTO, which is a rewrite of the earlier NET-FAQ for the new NET-2 TCP/IP code in Linux kernels 0.99.pl10 and above. The NET-2 code is the new kernel-based networking support for Linux, written by Fred van Kempen <waltje@uwalt.nl.mugnet.org>. It is based on the NET-1 code by Ross Biro <bir7@leland.stanford.edu>, device drivers by Donald Becker <becker@super.org>, SLIP drivers by Laurence Culhane <loz@holmes.demon.co.uk>, and the D-Link driver by Bj0rn Ekwall <bj0rn@blox.se>. The NET-2debugged code is maintained by Alan Cox <iiitac@pyr.swan.ac.uk>. Many others too numerous to mention have provided support, bug fixes, and help. This NET-2 HOWTO is by Terry Dawson and Matt Welsh. It covers setup and configuration of TCP/IP under Linux using NET-2. It also hopefully answers some of the many questions about the NET-2 code and common problems that people have. It does not cover using TCP/IP (i.e. using telnet, FTP, etc.) I'd like to keep this document as short as possible... :) 0.1 Disclaimer The NET-2 code is under development, which means that it may not be as stable and easy to configure as you may like it to be. code is relatively new and bug fixes are being posted every day, so if you run into a large number of problems just hang in there. The software is in two stages of development at the moment. The version supplied in the standard kernel distribution is version NET-2D and is being progressively debugged and made more stable by Alan, until NET-2E, which is currently undergoing Beta testing, is ready for general release. NOTE: In this document, `NET-2' does not refer to the Berkeley Software Distribution NET-2 release of BSD UNIX. Yes, the names are conflicting. In this HOWTO, `NET-2' refers only to the new generation of TCP/IP code in the Linux kernel. 0.2 Questions already? If you have general configuration questions, and you have been unable to find the answers after reading the other various HOWTO and FAQ files, then you would be best served to post them comp.os.linux.help, or, if you believe it to be specifically related the NET-2 kernel code, then you could post it to the NET mailing list. Please include as much relevant information as possible, there is nothing more annoying than to have a bug or problem reported without sufficient information to even begin searching for it. Version numbers and revisons of code, a detailed account of the problem, and the circumstances that caused it to happen are essential. Traces and debug messages where available should also be considered mandatory. If you have a question relating to the configuration of, or problems experienced with, _any_ linux distribution, regardless of whether it be SLS, Slackware, Yggadsril, TAMU, MCC, Pro, or other, please contact the people who created the distribution for support before attempting to report it to the list, or the NET-2 developers directly. The developers of the NET-2 code _cannot_ and _will not_ offer support for NET-2 as distributed in any form, other than as specified in this document, or as per distributed Alpha test instructions. Please do NOT bug the NET-2 developers directly unless you have a _development_-related issue (especially Fred: he has to pay $$$ for his e-mail access). To join the NET channel of the Linux-activists mailing list send mail to linux-activists-request@niksula.hut.fi with the line X-Mn-Admin: join NET at the top of the message body (not the subject). Note that the SLIP channel of the mailing list has been disabled and the NET channel should be used for SLIP discussions as well. Remember, keep in mind that the NET channel is for development discussions only. 0.3 Related documentation There is now a book from the Linux Documentation Project entitled `Linux Network Administration Guide' by Olaf Kirch. It covers all aspects of setting up and using networking under Linux, including TCP/IP, UUCP, mail, news, etc. This book supplements the NET-2 HOWTO and covers all of the other aspects of using TCP/IP. This guide simply covers setup of NET-2, i.e., "How to put your machine on the net." You should read the Ethernet HOWTO (from sunsite.unc.edu: /pub/Linux/docs/HOWTO) if you are using an Ethernet network with NET-2. The Ethernet HOWTO explains all of the ins and outs of using and configuring Ethenet devices for Linux. This NET-2 HOWTO supercedes the earlier ``Linux NET-FAQ'' by Phil Copeland and Matt Welsh. The NET-FAQ is for Linux kernels previous to 0.99.pl10, running the older version of the TCP/IP code. This document used to be called the NET-2-FAQ, before the Linux HOWTO project was underway. Thus, the NET-2-FAQ and the NET-2 HOWTO are the same. 0.4 New versions of this document New versions of this document can be retrieved via anonymous FTP from sunsite.unc.edu:/pub/Linux/docs or directly from me (terryd@extro.ucc.su.oz.au). It will also be posted to the newsgroups comp.os.linux.announce, comp.os.linux.help, and news.answers. You can find news.answers FAQ postings, including this one, archived on rtfm.mit.edu:/pub/usenet. 0.5 Feedback Please send any comments, updates, or suggestions to me, terryd@extro.ucc.su.oz.au. The sooner I get feedback about this document, the sooner I can update and correct it. If you find any problems with it, please mail me, instead of posting to one of the newsgroups. I may miss your corrections. Thanks. Please send any money to either Fred, Linus, or the Free Software Foundation. They have made this happen. 1. NET-2 Supported Functionality The NET-2 code is a complete kernel implementation of TCP/IP for Linux, including many features not found in the original networking code. NET-2 supports many popular Ethernet cards, real IP routing, SLIP (Serial Line IP) for TCP/IP connections over a serial line, such as the phone line via modem, and PLIP (Parallal Line IP) for local connection of two machines using your printer ports. 1.1 Supported Ethernet cards NET-2 supports the following Ethernet cards: 3com 3c503, 3c503/16 Novell NE1000, NE2000 Western Digital WD8003, WD8013 Hewlett Packard HP27245, HP27247, HP27250 (these drivers could do with more testing) The following clones are reported to work: WD-80x3 clones: LANNET LEC-45 NE2000 clones: Alta Combo, Artisoft LANtastic AE-2, Asante Etherpak 2001/2003, D-Link Ethernet II, LTC E-NET/16 P/N 8300-200-002, Network Solutions HE-203, SVEC 4 Dimension Ethernet, 4-Dimension FD0490 EtherBoard 16, D-Link DE-600, SMC Elite 16. Please see the Ethernet HOWTO for more complete information. As mentioned above NET-2 also supports SLIP in the kernel. Therefore if you don't have an Ethernet connection you can do TCP/IP over the phone line, provided you have a SLIP server nearby (many universities and businesses provide SLIP access to employees/students) and a compatible modem (usually 14.4 v.42bis, depending on your SLIP server). Two possible modems are the US Robotics Sportster, or the Infotel 144DF Internal. 2. Getting the NET-2 Software Before you can configure TCP/IP on your system you need to get the appropriate software. This includes the current version of the Linux kernel (0.99.pl14 or above), TCP/IP configuration programs and files (e.g., /etc/ifconfig, /etc/hosts), and finally a set of network application programs (such as telnet, ftp, rlogin, etc.). You may already have all of the items below. Check and make sure that you do. For example, some distributions come with all of the NET-2 configuration files, binaries, libraries, and kernel installed, so there's no reason to get the following files. Note: they may not be in the places specified in this HOWTO. If you DO have the NET-2 software already, skip to section 3 on configuration. If you do NOT have the NET-2 software, follow the directions below. The current kernel version is found in nic.funet.fi:/pub/OS/Linux/PEOPLE/Linus/linux-0.99.14.tar.gz. This is a gzipped tar file; .gz is the new extension used by gzip. If you have the old version of gzip, "zcat foo.gz | tar xvf -" works. The current libraries (libc-4.4.4), can be found in sunsite.unc.edu:/pub/Linux/GCC/image-4.4.4.tar.z. (You'll probably want to install the include files in inc-4.4.4.tar.z as well! See the READMEs there for details.) You'll need at least ver 4.4.2 to use NET-2, as there were problems with earlier versions that affected routing and netmasks. The current NET-2 configuration file distribution is in tsx-11.mit.edu:/pub/linux/packages/net/net-2/sources/net/net-010.tar.z. This package includes network configuraiton programs such as ifconfig, route, netstat etc. The TCP/IP application binaries and setup files are found in tsx-11.mit.edu:/pub/linux/packages/net/net-2/binaries. Get the three files in this directory: net-base.tar.z, net-std.tar.z, and net-ext.tar.z. As some of the internals of the networking code have changed, you will also need to get and install the files that are in the tsx-11.mit.edu:/pub/linux/packages/net/new-net-2 directory, as they correct some problems you will experience if you opt _not_ get and install them :) If you use shadowed password (Most SLS users do), then you may find that the standard network programs do not support them. There used to be a specially modified package of binaries about, but these were intended as a short term fix, and have been removed. Recent work on the standard libraries will mean that as of version 4.5.x of libc, the shadow password handling will no longer need to be in the application, and will be handled externally. I have been assured that 4.5.x is due for release shortly. 2.1 Unpacking the software You don't need to unpack any of the following if you already have all of the NET-2 software installed. First, unpack the kernel sources in /usr/src. This will put all of the kernel sources under /usr/src/linux (the usual place). # cd /usr/src # zcat linux-0.99.14.tar.z | tar xvf - Next, unpack the libraries. (The following is a summary, please read the detailed instructions that come with the libraries for complete installation details) # cd / # zcat image-4.4.4.tar.z | tar xvf - Now, make the links to the new libraries in /lib. BE VERY CAREFUL that you do not delete the previous links. Do everything in one step, as so: # ln -sf /lib/libc.so.4.4.4 /lib/libc.so.4 # ln -sf /lib/libm.so.4.4.4 /lib/libm.so.4 Next, unpack the net-base package, which contains the basic utils and configuration files in /etc. Note that net-base makes symlinks in /etc for all of your TCP/IP configuration files to /conf. Therefore, BE WARNED: Before you unpack the following tar files, make a backup of your files in /etc. Unpacking net-base will overwrite many of the files in /etc with symbolic links to other places. For example, /etc/hosts is a symlink to /conf/net/hosts. Why is this done? Because Fred's Linux/PRO distribution of Linux keeps all machine-specific configuration files in /conf. And because this is the way he does it, we may as well too. In general it makes things easier to locate. If you want to keep all of your net files in /etc, that's fine, but you'll have to put them there by hand. Make a backup of everything in /etc before you unpack net-base. Then unpack it from / (the root directory): # cd / # zcat net-base.tar.z | tar xvvofp - Also, unpack net-std.tar.z, which contains the network clients and daemons (e.g., telnet and telnetd). Unpack it from / as well: # cd / # zcat net-std.tar.z | tar xvvofp - If you wish to use tin (a newsreader), or DIG (the DARPA Internet Groper), unpack the net-ext package from /: # cd / # zcat net-ext.tar.z | tar xvvofp - Now unpack the fixed versions of rlogin/telnetd from the files: # cd /tmp # gzip -dc ftpd.tar.z | tar xvf - # gzip -dc telnet-rlogin.tar.z | tar xvf - you will then need to copy the binaries to where the old version currently live. Finally, unpack the net-010 package, which contains the sources for the TCP/IP setup programs (ifconfig, arp, route, etc.) and the configuration files. This is unpacked into /usr/src/net-010. # mkdir /usr/src/net-010 # cd /usr/src/net-010 # zcat net-010.tar.z | tar xvvofp - ** Important information for Shadow Password users ** If you are using the SLS distribution, then replace any blank passwords in /etc/passwd with :x: instead of ::. Otherwise rshd/rlogind will let anyone become these user ids. This is an SLS setup bug and will by default allow anyone remote access to your machine, with root priveledges! 2.2 Putting things in the right place With the standard NET-2 distribution, all of the configuration files are in /conf/net, with links in /etc. For example, /etc/hosts is a link to /conf/net/hosts. However, if you are using a standard pre-packaged distribution of Linux such as SLS, /conf/net probably isn't used... that is, /etc/hosts is just /etc/hosts. So, when I say "/conf/net/hosts", I mean "/etc/hosts", and vice versa. Just keep in mind that the TCP/IP software only looks in /etc and /usr/etc for configuration files. Therefore, it makes sense to keep all of your files in /etc and /usr/etc as they should be. HOWEVER, Fred has decided to put the files in /conf/net with LINKS in /etc. Either way, it doesn't matter. When we say "/etc/hosts", it doesn't matter if /etc/hosts is an actual file or a link to /conf/net/hosts. If you just unpacked NET-2 above (i.e. you don't already have the files from installing SLS), then you don't have the configuration files in /conf/net (you only have the symlinks in /etc). The easiest way to get the configuration files in /conf/net is to copy them from the net-010 distribution: # mkdir -p /conf/net # chown -R root.root /conf; chmod -R 755 /conf # cp /usr/src/net-010/etc/* /conf/net You should make sure that all of the symlinks to /conf/net in /etc can be resolved (that is, try to "more" or "cat" each file, make sure you don't get any errors). Also note that some files will be duplicated: for example, /etc/inetd.conf is a symlink to /usr/etc/inetd.conf. However, from the cp command above you also have a /conf/net/inetd.conf, which can be deleted (remember that all of the programs still look in /etc, not /conf. So whatever is in /etc is the file which is actually being used). 2.3 Creating the device interfaces In previous version it was necessary to create a number of device files for the NET-2 code. This is no longer the case. If you have any of the following files created you should delete them: rm /dev/net /dev/arp /dev/unix /dev/inet rm /dev/ip /dev/icmp /dev/tcp /dev/udp rm /dev/wd0 /dev/wd1 /dev/wd2 /dev/wd3 rm /dev/ec0 /dev/ec1 /dev/ec2 /dev/ec3 rm /dev/ne0 /dev/ne1 /dev/ne2 /dev/ne3 should clean them all. 3. Building the Kernel You're now ready to build the new 0.99.pl14 kernel with the NET-2 code enabled. 3.1 Configuring the NET-2 kernel code A 'make config' will take you through configuring the kernel Select the drivers you desire by answering 'yes' when prompted. Note, you will be prompted for "Network Device Support?", but the label after it might suggest that this is for Ethernet only, this is not the case, and you must answer 'yes' to this, even if you only desire the slip or plip drivers to be configured. You will be asked later about each of the ethernet drivers, slip and plip in turn. The Ethernet HOWTO also contains much useful information for configuring Ethernet devices in the kernel. 3.2 Building the kernel You can now build the kernel as you normally would (see the file /usr/src/linux/README if you've never done this before). Essentially this entails editing /usr/src/linux/Makefile to set root device and default display mode. (*Note: keyboard is now handled by loadable keymaps as of 0.99.pl10; grab the file keytable.tar.z from your nearest Linux ftp site). Finally do 'make dep' and 'make'. You now have a new 0.99.14 kernel with NET-2 set up. I wouldn't reboot it quite yet as we still have to configure the NET-2 programs before it will work correctly. 4. Configuring NET-2 TCP/IP The final step is to modify the various setup files to get NET-2 working. After this is ready you can boot your new kernel and go happily netting (if all goes well). In this section I'll describe each of the major TCP/IP setup files, what they do, and what you need to do to configure them. If you're using SLIP, see section 5.0 on configuring SLIP. The discussion below is for Ethernet connections only. SLIP users should FIRST read all of section 4.0 and then apply the changes discussed in section 5.0. 4.1 Before you begin Before you can configure NET-2 TCP/IP, you need to find out the following information about your network setup. Your network admins can tell you most of these things. * IP address: this is the unique machine address in dotted-decimal format. An example is 128.253.153.54. Your network admins will provide you with this number. If you're only configuring loopback mode (i.e. no SLIP, no ethernet card, just TCP/IP connections to your own machine---called "loopback") then your IP address is 127.0.0.1. * Your network mask ('netmask'). For performance reasons, it is desirable to limit the number of hosts on any particular segment of a network. If you have a large number of addresses allocated to you, you might break those addresses up into large chunks, and create subnetworks, and then allow each individual network segment be a subnetwork of the whole network. The network mask is a pattern of bits, which when overlayed onto an address on your network, will tell you which subnet that address lives on. This is very important for routing, and if you find, for example, that you can happily talk to people outside your network, but not to some people within your network, there is a good chance that you have an incorrect mask specified. Your network administrators will have chosen the netmask when the network was designed, and therefore they should be able to supply you with the correct mask to use. Most networks are class C subnetworks which use 255.255.255.0 as their netmask. Other Class B networks use 255.255.0.0. The NET-2 code will automatically select a mask that assumes no subnetting as a default if you do not specify a mask. The masks chosen by default are as follows: For addresses with the first byte: 1-127 255.0.0.0 (Class A) 128-191 255.255.0.0 (Class B) 192+ 255.255.255.0 (Class C+) If one of these doesn't work, try the other. If this doesn't work, ask your local net guru for help. This applies equally well to the loopback port. Since the loopback ports address is always 127.0.0.1, the netmask for this port is always 255.0.0.0. You can either specify this explicitly or rely on the default mask. * Your network address. This is your IP address masked with the netmask. For example, if your netmask is 255.255.255.0, and your IP address is 128.253.154.32, your network number (IP addr AND netmask) is 128.253.154.0. With a netmask of 255.255.0.0, this would be 128.253.0.0. If you're only using loopback, you don't have a net address. * Your broadcast address. This is your IP address masked with the netmask, and then possibly ORed with the subnetmask inverted. Such that for a Class C network, with netmask 255.255.255.0, your broadcast address will be your network address (calculated above) ORed with 0.0.0.255. For example: Your IP address is: 128.253.154.32 Your netmask is: 255.255.255.0 netmask inverted is: 000.000.000.255 then: Your broadcast address should be: 128.253.154.255. Note that for historical reasons, some networks are setup to use the network address as the broadcast address, if you have any doubt, check with your net admin. If you have access to a sniffer, or some other device capable of providing a trace of your network, then you might be able to determine both the network and broadcast addresses by looking at the traffic on your network. Keep an eye open (or filter all traffic except) for ethernet frames destined for the ethernet broadcast address: ff:ff:ff:ff:ff:ff, if it is an IP datagram, then look at the destination ip address. If the IP source address is your router, and the protocol ID is not ARP, then what you are seeing might be a routing broadcast. The destination IP address in this case will be the IP broadcast address of your network. You can then work out the IP network address. But again, if in doubt then consult your network admin, or check the configuration of a known working machine. If you're only using loopback, you don't have a broadcast address. * Your gateway address. This is the address of the machine which is your "gateway" to the outside world (i.e. machines not on your subnet). In general the gateway machine has an IP address identical to yours but with a ".1" in the last position; e.g. if your IP address is 128.253.154.32, your gateway might be 128.253.154.1. Your network admins will provide you with the IP address of your gateway. If you're only using loopback, you don't have a gateway address. If your network is not connected to the Internet, that is, it is a standalone network, then you don't have a gateway, and therefore don't need a gateway address. * Your nameserver address. Most machines on the net have a name server which translates hostnames into IP addresses for them. Your network admins will tell you the address of your name server. You can in fact run a nameserver on your own machine by running named, in which case the nameserver address is 127.0.0.1. However, But it is not required that you run named at all; see section 4.2.2.1. If you're only using loopback, you don't have a nameserver address. (After all, you're only connecting to yourself.) NET-2 supports full routing, multiple routes, subnetworking (at this stage on byte boundaries only), the whole nine yards. The above describes most basic TCP/IP configurations. Yours may be quite different: when in doubt, consult your local network gurus and check out the man pages for "route" and "ifconfig" included with the net-010 package. Configuring TCP/IP networks is very much beyond the scope of this document; the above should be enough to get most people started. 4.2 /etc/rc.d/rc.inet1 and /etc/rc.d/rc.inet2 For the non-UNIX wizard: "rc" files are run at bootup time by the "init" program and start up all of the basic system programs, such as sendmail, cron, etc. as well as the NET-2 daemons (such as inetd). For NET-2 the rc files are found in /etc/rc.d. It doesn't really matter where you keep them, as long as init can find them. (We'll go into this later). First things first. The file /etc/rc.d/rc.inet1 configures the basic TCP/IP interface to your machine, using two programs: /etc/ifconfig and /etc/route. These two programs tell the kernel how to route and manage TCP/IP connections to your system, by setting things such as the IP address, network mask, and so on. Note that in the previous NET-1 code, the "config" program was used. However, the "standard" for UNIX system TCP/IP configuration is to use ifconfig and route, and this has been implemented with NET-2. THEREFORE: Get rid of your old "rc.net" if you have one. You should only run rc.inet1 and rc.inet2 at boot time. If you run your old "rc.net" instead, you'll get error messages about "old-style ioctl" and things probably won't work at all. NOTE: SLS uses "rc.net" instead of "rc.inet1" and "rc.inet2". Just make sure that your "rc.net" uses "ifconfig" and "route" instead of the old "config" program. In other words, be sure that your rc.net is a new, NET-2 style rc.net. If it is not, get rid of it and replace it with rc.inet1 and rc.inet2, as described below. If you run SLS, the file "rc.net" contains the code for both rc.inet1 and rc.inet2. Below you're going to edit rc.inet1 to use the correct ifconfig and route commands for your machine. But first, you need to know the information about your network setup in section 4.1, above. 4.2.1 Editing rc.inet1 Edit the file /etc/rc.d/rc.inet1. This file uses the "ifconfig" and "route" commands to configure your network interface at boot time. Remember that SLS uses just rc.net. You may need to do some heavy surgery on this file to get it to look right; it may be easier to delete it and start from scratch. Given the information above, a possible rc.inet1 should look like: #!/bin/sh # rc.inet1: configure the network interface HOSTNAME=`hostname` # Attach the loopback device. /etc/ifconfig lo 127.0.0.1 # uses default netmask 255.0.0.0 /etc/route add 127.0.0.0 # Network address for loopback network # IF YOU HAVE AN ETHERNET CONNECTION, use these lines below to configure the # eth0 interface. If you're only using loopback or SLIP, don't include the # rest of the lines in this file. # Edit for your setup. IPADDR="128.253.154.32" # REPLACE with YOUR IP address! NETMASK="255.255.255.0" # REPLACE with YOUR netmask! NETWORK="128.253.154.0" # REPLACE with YOUR network address! # Note: NETWORK MUST be in # /etc/networks BROADCAST="128.253.154.255" # REPLACE with YOUR broadcast address, if you # have one. If not, leave blank and edit below. GATEWAY="128.253.154.1" # REPLACE with YOUR gateway address! /etc/ifconfig eth0 ${IPADDR} netmask ${NETMASK} broadcast ${BROADCAST} # If you don't have a broadcast address, change the above line to just: # /etc/ifconfig eth0 ${IPADDR} netmask ${NETMASK} /etc/route add ${NETWORK} # MUST HAVE AN ENTRY IN # /etc/networks !!! /etc/route add default gw ${GATEWAY} metric 1 # Add this line only if your # network is not standalone # End of rc.inet1 This is a basic rc.inet1 to run the ifconfig and route commands needed to set up a basic TCP/IP connection. Edit this for your setup. To ensure that this will be run at boot time, make sure that you include the command /bin/sh /etc/rc.d/rc.inet1 in your /etc/rc, or in your /etc/inittab (if you're running the sysvinit package). In general, make sure that rc.inet1 is run BEFORE rc.inet2 at boot time. You may wish to run rc.inet1 and rc.inet2 from /etc/rc or /etc/rc.local. Or you can run them from /etc/inittab. Either way is fine, but don't run one without the other. 4.2.2 Editing rc.inet2 The rc.inet2 script is also run at boot time, AFTER rc.inet1. It starts up various TCP/IP daemons such as inetd, portmapper, and so on. Remember that SLS uses just rc.net. You will probably want to comment out most of this file, especially if you're not planning on using NFS (Network File System). You MUST leave the stanza to run inetd and syslogd uncommented. Note that if you DON'T uncomment everything but inetd and syslogd, you may run into network problems at first. The best bet is to comment all of these things out, get yourself on the network, and then worry about configuring the rest of the clients in rc.inet2. If you're not going to be using NFS, you can comment out the lines to run: ugidd, mountd, nfsd, pcnfsd, and bwnfsd. You can comment out the stanza to run "umail" unless you have that package. In general, most of the things found in rc.inet2 are "sold separately". I recommend starting only inetd and syslog at first until you get everything going. 4.2.2.1 "To named or not to named... that is the question." Named is the nameserver daemon that runs under TCP/IP. It allows your machine to serve the name lookup requests of other machines... that is, if a machine wants to find the IP address for "goober.norelco.com", and you have this machine's IP address in your named database, then you can service the request and tell other machines what goober's address is. Under older implementations of Linux TCP/IP, to create aliases for machine names (even for your own machine), you were required to run named on your Linux box to store name->IP address translations. The problem with this is that named is generally difficult to setup and maintain. To solve this problem, a program called "hostcvt.build" was made available on Linux systems to translate your /etc/hosts file (see section 4.3) into named database files. However, even with this problem out of the way, running named on your system will cause some amount of CPU load and network traffic. The bottom line is this: You DO NOT need to run named on your Linux system. The SLS instructions will probably tell you to run hostcvt.build to set up named. This is simply unnecessary, UNLESS you want to make your Linux system a nameserver for some reason. Now, instead of putting hostnames into the named database, you can simply include them in the file /etc/hosts (section 4.3). When looking up names, your Linux system will first look in /etc/hosts and then ask the nameserver out on the net (if you have one). The only reason you may want to run named would be if: a) You're setting up a network of machines, and need a nameserver for one of them (and don't have a nameserver out on the net elsewhere); b) Your network admins want you to run your Linux system as a nameserver for some reason; or, c) You have a slow SLIP connection, and want to run a small cache-only nameserver on your Linux machine so that you don't have to go out on the phone line every time a name lookup occurs. (If you are only going to lookup a small number of machine names, and you know what they are, you can put their addresses in /etc/hosts instead.) Generally name lookup isn't that slow, and should work fine over most SLIP connections. d) You want to run a nameserver for fun and excitement. In general, you DO NOT need to run named: this means that you can comment it out from rc.inet2, and you don't have to run hostcvt.build. If you want to alias machines, for example you want to refer to "loomer.vpizza.com" just as "loomer", you can add an alias in /etc/hosts instead. There is no reason to run named unless you truly want a full nameserver on your machine. If you already have a nameserver (most machines on the Internet do, and your net admins will tell you its address), don't bother running named. If you're only using loopback, you can run named and set your nameserver address to 127.0.0.1, but that's pointless. (No pun intended.) You don't need a nameserver at all if you use only loopback; the only hostname you know is your own, and it's in /etc/hosts (see section 4.3, below). 4.3 /etc/hosts /etc/hosts contains a list of IP addresses and the hostnames they map to. In this way, you can refer to other machines on the network by name, as well as by IP address. Using a nameserver (see section 4.1) also allows you to do the name->IP address translation automatically. (Running named allows you to run your own nameserver on your Linux box. See section 4.2.2.1 above.) This file needs to contain at least an entry for 127.0.0.1 with the name "localhost". If you're not only using loopback, you need to contain an antry for your IP address, with your full hostname (such as loomer.vpizza.com). You may also wish to include entries for your gateway and network addresses. For example, if "loomer.vpizza.com" has the IP address "128.253.154.32", my /etc/hosts file would look like: # /etc/hosts: List of hostnames and IP addresses 127.0.0.1 localhost 128.253.154.32 loomer.vpizza.com loomer # end of hosts Once again, edit this for your own needs. If you're only using loopback, the only line in /etc/hosts should be for 127.0.0.1, with both "localhost" and your hostname after it. Note that in the second line, above, there are two names for 128.253.154.32: "loomer.vpizza.com" and just "loomer". The first name is the full hostname of the machine. The second is an alias---it allows me to just use "rlogin loomer" without having to type in the entire name. 4.3.1 Important note The line "%%IP%% %%HOST%% %%ALIAS%%" needs to be deleted from this file! This is a "tag" line used by Fred's experimental net config scripts. Matt Welsh is now writing a new set of scripts which don't use these lines. In any of these files, you see curious lines with entries such as "%%NAME%%", these lines MUST be deleted. If you don't delete them, you may have lots of strange errors and overflowing syslog files. 4.4 /etc/networks The /etc/networks file lists the names and addresses of your own, and other, networks. It is used by the route command, and allows you to specify a network by name, should you so desire. Every network you wish to add a route to using the 'route' command MUST have an entry in /etc/networks Its format is similar to that of the /etc/hosts file, (Sec 4.3) and an example one might look like: # # /etc/networks: list all networks that you wish to add route commands # for in here # default 0.0.0.0 # default route - mandatory loopnet 127.0.0.0 # loopback network - mandatory mynet 128.253.154.0 # Example network CHANGE to YOURS # # end of networks 4.5 /etc/host.conf This file specifies how your system will lookup names. It should contain the two lines: order hosts,bind multi on These two lines tell the resolve libraries to first check the /etc/hosts file for any names to lookup, and then ask the nameserver (if one is present). The "multi" entry allows you to have multiple IP addresses for a given machine name in /etc/hosts. This file comes from the implementation of the resolv+ bind library for Linux. You can find further documentation in the resolv+(8) man page (if you have the man page available). 4.6 /etc/resolv.conf This file contains two types of entires: The addresses of your nameservers (if any), and the name of your domain (if you have one). If you're running your own nameserver (i.e., you're running named on your Linux machine: see section 4.2.2.1), then the address of your nameserver is just 127.0.0.1 (the loopback address). Your domain name is your fully-qualified hostname (if you're a registered machine on the Internet, for example), with the hostname chopped off. That is, if your full hostname is loomer.vpizza.com, your domain name is just "vpizza.com", without the hostname ("loomer"). For example, if your machine is goober.norelco.com, and has a nameserver at the address 128.253.154.5, your /etc/resolv.conf would look like: domain norelco.com nameserver 127.253.154.5 You can specify more than one nameserver. Each one must have a "nameserver" line of its own in resolv.conf. If you're only using loopback, you don't have a nameserver. 4.7 /etc/HOSTNAME This is a new file; it contains the full hostname of your machine (with the domain name). For example, the machine above would have the file /etc/HOSTNAME: goober.norelco.com That's all. 4.8 /etc/rc.local Change the line in /etc/rc.local (or /etc/rc, depending on your setup) which sets your system's hostname, to /bin/hostname -S (You have a new hostname in /bin.) This sets your hostname from the name found in /etc/HOSTNAME. If you don't like this (personally I don't), just do: /bin/hostname -S <your-hostname> For example, /bin/hostname -S loomer.vpizza.com It IS important that you give a full hostname (with domain name) in /etc/HOSTNAME. This allows the hostname command to set the host AND domainname in one shot. IMPORTANT: The hostname found in /etc/HOSTNAME *must* be a valid hostname. This means that it must be found in /etc/hosts (or that your nameserver must be able to resolve it, but you should put it in /etc/hosts in case your nameserver is down). 4.9 Other files There are of course many other files in /etc which you may need to dabble with later on. Instead of going into them here, I'm going to provide the bare minimum to get you on the net. More information will be provided in later versions of the NET-2 HOWTO. Once you have all of the files set up, and everything in the right place, you should be able to reboot your new kernel and net away to your heart's content. However, I strongly suggest that you keep a bootable copy of your old kernel and even possibly a "recovery disk" (say, the SLS a1 disk, or HJLu's single disk boot disk) in case you hosed your /etc/rc files, for example, and can't login when you boot. 5. Configuring SLIP SLIP (Serial Line Internet Protocol) allows you to use TCP/IP over the phone line, with a modem (no need for an Ethernet card). Of course, to use SLIP you'll need access to a dial-in SLIP server in your area. Many universities and businesses provide SLIP access all over the world. Configuring SLIP is much like configuring an Ethernet interface (please read section 4.0 above). However, there are a few key differences. First of all, dialing in and connecting to your SLIP server is usually done at boot time, usually by a program called "dip" (found in the "dip" subdir of the net-010 package). "Dip" not only dials and logs you into the SLIP server, but it also initiates the SLIP connection and runs the appropriate ifconfig and route commands to initialize the device. Therefore, the only lines needed in /etc/rc.d/rc.inet1 are the few commands to initilize the loopback connection at the top (see section 4.2.1 above). If you're not using DIP, you may indeed have to edit rc.inet1 for your SLIP parameters. Also, there are two types of SLIP servers: Dynamic IP address servers and static IP address servers. Dynamic servers allocate a new, different IP address to you every time you dialin and initiate a connection. Static servers give you the same address every time. Almost every SLIP server will also prompt you for a username and password when dialing in: DIP can handle logging you in automatically. Essentially, configuring a SLIP connection is just like configuring for loopback or ethernet. The main differences are discussed below. Read section 4.0 above for information on configuring your TCP/IP files, and apply the changes below. 5.1 Static SLIP server connections If you have a static-allocation server (same IP address every time), then you may want to put entries for your hostname and IP address (since you know what your IP address is!) in /etc/hosts. You should also configure the other files listed in section 4.0: rc.inet2, host.conf, resolv.conf, /etc/HOSTNAME, and rc.local). Remember that when configuring rc.inet1, you don't need to run the ifconfig and route commands other than the two for the loopback interface (if you're using DIP to dial your connection). In general, your gateway is the IP address of your SLIP server. Because DIP handles the configuration of the route, you probably don't need to know this, but in some cases you might have to run the appropriate ifconfig or route commands in /etc/rc.d/rc.inet1 to get it to work correctly. Instead of using "eth0" as your interface name, SLIP connections use "sl0". Keep in mind that you can't ifconfig sl0 until you have dialed the connection and connected to the SLIP server. Also, you may need to use the "pointopoint" argument to ifconfig if DIP does not do it correctly. For example, if your SLIP server's address is 44.136.8.5, and your IP address is 128.253.154.32, you may need to run the command # /etc/ifconfig sl0 128.253.154.32 pointopoint 44.136.8.5 See the man pages for ifconfig in the net-010 package. 5.2 Dynamic SLIP server connections If your SLIP server allocates a new IP address to you every time you dialin, you don't know your IP address at all, so you can't include an entry in /etc/hosts for your machine. (If you want, you can place your hostname in /etc/hosts with the address 127.0.0.1). Most dynamic SLIP servers tell you your IP address when you initiate the connection. For example, it may print a string such as, "Your IP address is 128.253.154.10. Server address is 128.253.154.1." DIP will need to know these numbers when it configures the connection. See section 5.3 below on using DIP. If you use DIP, it does all of the work of configuring the connection when you dialin, so rc.inet1 only needs the two lines to configure the loopback address (see section 4.2.1 above). Also, see section 5.1 above. You need to configure all of the files listed in section 4.0. Your gateway address (should you need to know it) will be the address of the SLIP server. Also, you may need to run ifconfig on sl0 using the SLIP server's address as the "pointopoint" argument (see section 5.1 above). However, if you use DIP, it should be able to do all of the ifconfig and route commands for you. One good way to figure out how to configure SLIP on your machine is to find someone else who uses the SLIP server (it can be on a PC, Mac, UNIX box, whatever) and find out what numbers they use. 5.3 Using DIP DIP can simplify the process of dialing into the SLIP server, logging in, starting the connection, and configuring the sl0 device with the appropriate ifconfig and route commands. Essentially, to use DIP you'll write a "chat script" which is basically a list of commands to send to DIP along with commands for logging in, starting the connection, and so on. See "sample.dip" in the net-010 package for an explanation. DIP is quite a powerful program, with many options. Instead of going into all of them here you should look at the READMEs and the sample files from tsx-11 and the net-010 distribution. You may notice that the sample.dip script assumes that you're using a static SLIP server, so you know what your IP address is beforehand. For dynamic SLIP servers, you'll probably need to use the command "dip -t" and use the DIP "local" and "remote" commands by hand after the SLIP server prints your IP address. For example, loomer:~% dip -t DIP>port cua0 (My modem is on /dev/cua0.) DIP>speed 57600 (Set the baud rate.) DIP>reset (Reset modem and terminal line.) DIP>send att\r\n (Send modem init string...) DIP>dial 2446000 (Dial SLIP server.) DIP>term (Enter interactive mode.) Welcome to Annex Server... Annex login: mdw1 Annex password: User mdw1 authenticated. Annex> slip (From SLIP server prompt, give "slip" command to start SLIP connection.) SLIP inititated. Your IP address is 128.254.254.10, server address is 128.254.254.1. ^] (Hit DIP break key to get back to DIP prompt.) DIP> local 128.254.254.10 (Give local command to specify my IP address.) DIP> remote 128.254.254.1 (Specify server's IP address.) DIP> mtu 1500 (Set SLIP MTU value.) DIP> mode SLIP (Start the SLIP mode from DIP.) loomer:~% Now we're running in SLIP mode, and everything should work. The command # /etc/ifconfig sl0 will tell you the current interface parameters; you may need to set some of these by hand if DIP didn't get the correctly. Also, some have found that they need to use the route command to change their operating parameters. DIP sets a route for the address of your SLIP server, but you may need to delete this route and add it as your gateway instead. For example, with a SLIP server address of 128.253.154.1, use the commands: # /etc/route del 128.253.154.1 # /etc/route add default gw 128.253.154.1 In later versions of dip, and I too profess to be confused as to exactly which version it might be, this procedure will not work, and you should instead use the dip default command instead. This will automatically point your default route via your slip link. It should be simple to modify the code for DIP in the file attach.c to run the route and ifconfig commands that work for you automatically. Of course, typing all of those DIP commands may be time consuming. It may be possible to write a DIP chat script to run all of the commands up through dialing the connection and logging in, and then "exit" the script to let you type the "local" and "remote" commands by hand. Furthermore, there are patches for DIP by Paul Mossip (mossip@vizlab.rutgers.edu) which modify the "get" command to grab the IP address of your host and the server from the output of the SLIP server. This should allow you to do all of the dialing and configuration within a chat script just as you would with static SLIP servers. This patch was recently posted to comp.os.linux.announce. (Check the c.o.l.a archives on sunsite.unc.edu.) Fred is planning to modify DIP for easier use by those with dynamic SLIP servers (including the above patch) soon. You'll have to play with various values for your routes and gateways to get everything going correctly. If you have any information on how you configured your SLIP interface, please drop me a note (terryd@extro.ucc.su.oz.au). Include info on your SLIP address, server address, gateway, and so on, and what commands you used to set up SLIP. There are various possible configurations for SLIP servers and I'd like to update this NET-2 HOWTO with as many hints as possible. :) 5.4 Configuring your Linux Machine as a SLIP Server So, you wanna go bleeding edge eh ? Ok. I've asked Fred about how to do this, and the following is what he has supplied. What I would like you to do is take the following information, and make what use of it you can. Then, when you have a slip server successfully working, I'd like you to send me your configuration scripts, and a description of how to use it, and send it to me to replace this section. Ok ? Note: Some of the information below came from the dip man pages, where in fact how to run Linux as a slip server is briefly documented. To configure Linux as a slip server, you need to create Special slip accounts for users, where dip (in slave mode) is used as the login shell. Fred suggests that he has a convention of having all of his Slip accounts begin with a capital 'S', eg "Sfredm". A sample /etc/passwd entry for a Slip user looks like: Sfredm:ij/SMxiTlGVCo:1004:10:UUNET:/tmp:/usr/bin/dip -i ^^ ^^ ^^ ^^ ^^ ^^ ^^ | | | | | | \__ dip as login shell | | | | | \_______ Home directory | | | | \_____________ User Full Name | | | \__________________ User Group ID | | \______________________ User ID | \________________________________ Encrypted User Password \___________________________________________ Slip User Login Name After the user logs in, the login(1) program, if it finds and verifies the user ok, will execute the dip command in input mode (-i). Dip now scans the /etc/net/diphosts file for an entry for the given user name. Therefore, each slip user must also have an entry in /etc/net/diphosts. 5.5 /etc/net/diphosts /etc/net/diphosts is used by dip to lookup preset configurations for remote hosts. These remote hosts might be users dialing-into your linux machine, or they might be for machines that you dial into with your linux machine. The general format for /etc/net/diphosts is as follows: Suwalt::145.71.34.1:SLIP uwalt:CSLIP,1006 ^ ^ ^ ^ ^ ^ | | | | | \___ MTU | | | | \_________ protocol (SLIP, CSLIP, | | | | KISS, PPP) | | | \___________________ comment field ("gecos" :-) | | \________________________________ IP address of the other | | side, or host.domain.name | \___________________________________ unused (compat. with passwd) \________________________________________ login name (as returned by getpwuid(getuid()) ) An example /etc/net/diphosts entry for a remote slip user might be: Sfredm::145.71.34.1:SLIP uwalt:SLIP,296 which specifies a SLIP link with MTU==296, or Sfredm::145.71.34.1:SLIP uwalt:CSLIP,1006 which specifies a CSLIP-capable link with MTU of 1006. 5.6 Configuring Plip interfaces PLIP is like SLIP, in that it is used for providing point to point IP links between machines, except that it is designed to use the Parallel ports on your machine instead of the serial ports. Because it is possibel to transfer more than one bit at a time with the Parallel port, it is possible to attain higher speeds with the plip interface than with the serial interface. In addition, even the simplest of parallel ports, printer ports, can be used, in lieu of you having to purchase conmparatively expensive 16550AFN UARTs for your serial ports. When compiling the kernel, there is only one file that might need to be looked at. That file is net/drv/plip/global.h, and it contains timers in mS. The defaults are probably going to be fine, unless you have an especially slow computer, in which case you might have to increase them on the machine at the other end of the link. A sample configuration for a dip interface might be: /etc/rc.d/rc.inet1: ifconfig pl0 192.148.64.1 broadcast 192.148.255.255 \ netmask 255.255.0.0 pointopoint 212.194.167.1 up The pointopoint parameter has the same meaning as for SLIP, in that it specifies the address of the machine at the other end of the link. /etc/rc.d/rc.inet2: route add default pl0 metric 1 In almost all respects, you can treat a plip interface as though it were a slip interface, except that dip is not, and cannot be used. 5.6.1 PLIP Cabling Diagram PLIP has been designed to use cables with the same pinout as those commonly used by the better known of the dos based pc-pc file transfer programs. The pinout diagram (taken from net/drv/plip/README) looks as follows: GROUND 25 - 25 D0->ERROR 2 - 15 15 - 2 D1->SLCT 3 - 13 13 - 3 D2->PAPOUT 4 - 12 12 - 4 D3->ACK 5 - 10 10 - 5 D4->BUSY 6 - 11 11 - 6 D5 7* D6 8* D7 9* STROBE output 1* AUTOFD output 14* INIT output 16* SLCTIN output 17* Do not connect the pins marked with an asterisk (`*'). They are D5 (pin 7), D6 (pin 8) and D7 (pin 9). STROBE is pin 1, FEED is pin 14. Extra grounds are on pins 18, 19, 20, 21, 22, 23 and 24. If the cable you are using has a metallic shield it should be connected to the metallic DB-25 shell at one end only. 6. Are You Stuck? Really? Then you should read the man pages for ifconfig and route, included in the net-010 package, and understand their functions. These commands have a lot of flexibility, and because everyone's network setup is different, you may find a way to use ifconfig and route to get your connection working. If you do, feel free to send me some mail so I can include it in the next update of the NET-2 HOWTO. Because of my limited amount of experimental data, most of the discussion above is about my own setup, and I'd like to generalize it as much as possible. Matt is currently writing a set of scripts to simplify NET-2 configuration. You can pick up the pre-alpha release from tc.cornell.edu, in the file /pub/mdw/netconf-0.3.tar.z. These scripts maintain a small database of network configuration info, and allow you to easily modify and configure your network interface. The scripts are far from complete: Matt has been waiting until the NET-2 interface itself stabilizes a bit more before upgrading it further. Another good place to look for help on setting up NET-2 is the O'Reilly and Associated book ``TCP/IP Network Administration''... the one with the crab on the cover. Keep in mind that NET-2 is now a "standard" implementation of TCP/IP---this means that ifconfig and route work the same under Linux as they do on other UNIX systems. You might also search out the following documents which are an excellent source of tutorial information on tcp/ip: athos.rutgers.edu:/runet -rw-r--r-- 1 0 0 176218 Oct 20 1989 tcp-ip-admin.doc -rw-r--r-- 1 0 0 214199 Oct 20 1989 tcp-ip-admin.ps -rw-r--r-- 1 0 0 92106 Oct 20 1989 tcp-ip-intro.doc -rw-r--r-- 1 0 0 111478 Oct 20 1989 tcp-ip-intro.ps Also keep in mind that NET-2 _is_ developing very rapidly---it's one of the newest additions to the Linux kernel. Thus, all of the bugs haven't been worked out yet, so there may be some problems. However, a good rule of thumb is that if you were able to get TCP/IP working under kernels before 0.99.pl10, you should be able to get it working under NET-2 as well. There are still some issues dealing with performance to be fixed, but overall the system works. And, as with everything in Linux development, time will cure what ails NET-2. If it's absolutely unusable to you, go back to an earlier kernel version, and wait until things develop further. The code is still fairly new. 7. Common Problems and Solutions Now that the NET-2 HOWTO has been out for a while, I've been able to gather some common problems (and answers!). Here are some things which I have learned from hearing from readers. If you run into a problem which should be included here, please send it along (even if you have the solution!). QUESTION: Whan I try to use the network, or use SLIP, I get the error message "Network not reachable". What should I do? ANSWER: This message means that a machine somewhere in the path did not have a route to the destination network. Until you can demonstrate otherwise, it is the courteous thing to do, assume it is your machine. This is usually an indication that either your ifconfig or route commands are in some way wrong. You can look at the status of your ifconfig by using the command "ifconfig" by itself. This should tell you what NET-2 thinks your IP address, netmask, etc. are. You can use the command "route" by itself to get routing information. This will tell you what routes you have set up and what gateways (if any). The best way to test a SLIP or network connection is to use "ping" with IP addresses only. If you use hostnames, as in "ping loomer", if some part of name lookup isn't working you'll have trouble. To test just the network, NOT name lookup, use only IP addresses, as in "ping 128.253.154.32". For SLIP connections the best thing to do is to ping your SLIP server. If nothing comes back, then something is wrong. Try using "dip -v" which will print debugging information while DIP is dialing the server. Remember that for some SLIP connections you may need to use the commands # route del <your slip server address> # route add default gw <your slip server address> or the dip: default command (depending on the version of dip you are running), to get SLIP talking to the server. Once you can talk to the server, everything SHOULD work (if your server is set up correctly!). For Ethernet connections, try pinging your gateway. If you can talk to your gateway, you should be able to talk to the outside world. You may need more than one route (that is, more than one gateway). For example, some universities use one gateway for on-campus networks and another for off-campus networks. Either way, try pinging addresses on your local network, and remote addresses. If you can ping all addresses ok remote to your network, and some on your local network, but not others on your local network, then check your netmask setting. If the "network not reachable" message means that you can't talk to your gateway. This can be due to several things: a) Wrong route or ifconfig commands b) Ethernet card problems (see below) c) You didn't compile the kernel correctly (see below). d) There is in fact some sort of network failure elsewhere. QUESTION: I keep getting the error "eth0: transmit timed out". What does this mean? ANSWER: This usually means that your Ethernet cable is unplugged, or that the setup parameters for your card (I/O address, IRQ, etc.) are not set correctly. Check the messages at boot time and make sure that your card is recognized with the correct Ethernet address. If it is, check that there is no conflict with any other hardware in your machine, eg you might have a soundblaster sharing the same IRQ or i/o control port. QUESTION: I get errors "check Ethernet cable" when using the network. ANSWER: You probably have your Ethernet card configured incorrectly. For Etherlink cards, in the file /usr/src/linux/net/inet/CONFIG, change the line EL_OPTS = -UEL2_AUI to EL_OPTS = -DEL2_AUI This tells the card to use the AUI cable interface. Just make sure that all of the options for your card are set correctly in the CONFIG file, and rebuild your kernel. QUESTION: When I use NET-2, I get a "General protection" error or a panic from the kernel. How can I fix this? ANSWER: Remember that the NET-2 code is still on the buggy side, just because it's in mid-development. If you get a kernel panic while using NET-2, write down the EIP address (and the other information given in the panic message). The EIP is the address where the kernel paniced, usually of the form 0008:xxxxxxxx where "0008" is the segment descriptor for the kernel text, and "xxxxxxxx" is the offset into that segment (80386 programmers will know what this means). Use the command nm /usr/src/linux/tools/system | sort -n or nm /usr/src/linux/tools/zSystem | sort -n depending on whether or not you use a compressed kernel (zImage). This will print a listing of all symbols in the kernel text, simply scan down the list and look for the function that contains the EIP address in the kernel dump. There's the culprit. However, in some cases the EIP can be misleading; the kernel may panic at a place which is complete irrelevant to where the actual problem occurred. However, it is a good starting place; first, locate the function which contains the EIP address, and then check out the kernel code to see what might be wrong. Keep in mind that this will only work if you compile your own kernel and have the "system" file associated with it. QUESTION: How can I hang up the phone line when I'm done using SLIP? ANSWER: If you use dip to dial out on the SLIP line, just "kill -9" the dip process itself (dip won't die unless you kill it with SIGKILL or some other signal). When dip dies, the line should hang up. If you don't use dip to dial out, either instruct your dialing program to hang up the line, or kill the dialing process. QUESTION: With SLIP, I get a connection open, but no data flows. ANSWER: This could be a number of things. First, check your routes and be sure that the gateway is set correctly. Attempt to ping your gateway; if you can't, then something is wrong with the routes. Another problem could be that your system and the SLIP server disagree about header compression. With 0.99.pl11 and above, SLIP automatically compresses packet headers. To turn off header compression, check the SL_COMPRESS option in the CONFIG file. In pl14 there will be supplied a 'setencap' command to allow you to configure compression. QUESTION: With SLIP, I get a connection, but after sending a small amout of data, the connection hangs. ANSWER: Probably an MTU problem. The MTU is the maximum packet size available for the network. For SLIP, your MTU is set in your dip dialing script with the "MTU" command. The default value is 1500, which means that the system can send packets of up to 1500 bytes in size. However, some SLIP servers (Berkeley SLIP, for example), use a smaller MTU (around 1006). If your MTU is too large, the SLIP server will fragment the packets, and currently (NET-2d), IP packet fragmentation isn't supported (see next section). The solution is to set a smaller MTU (around 512, or lower) in your dip chat script. Another thing to check if you are having erratic SLIP problems is flow control. You need to use hardware (RTS/CTS) flow control on your modem, and your modem and your computer must agree. XON/XOFF flow control is not practical for SLIP. 8. Known bugs There are several known bugs with the NET-2 software. Note that these may or may not be fixed with a newer version of the NET-2 code; therefore, I leave them here. The bugs here are for NET-2d, found in kernels 0.99.pl10, pl11, and pl12, and pl13, and pl14. NET-2e (currently in Beta), when released, may or may not have fixed these bugs. * Bug with route guessing code. If you ifconfig the "lo" interface before the "eth0" interface in rc.inet1, whenever you add a route, it will be added to "lo" instead of "eth0". (Simply use the "route" command by itself; it will display all of your routes. If your "default" route, which should be out on the ethernet, is for device "lo" instead of "eth0", then you're seeing this bug.) This is just a problem with the route guessing code. Several things can fix it: 1) ifconfig/route on "eth0" before "lo" in rc.inet1; or, 2) Set your netmask to 255.0.0.0 (which is reported to work, but I can't guarantee it). This should be fixed in NET-2e. * Missing IP packet fragmentation. Packet fragmentation allows the various protocol layers to "chop up" packets into smaller packets if the MTU (maximum tranfer unit) of one network differs from another. NET-2e should contain packet fragmentation/defragmentation code, but NET-2d currently does not. pl14 has had fragmentation support fitted. * Weak NFS support. There have been a number of success stories with NFS under Linux, however, not all of the support is there. For one thing, the current NFS buffer size is much smaller---and therefore much slower---than other implementations of NFS. From what I understand, this problem is related to the lack of packet fragmentation code, above. With pl14 and upwards this will probably be resolved. 9. Miscellaneous I'm sure that I've missed something. This NET-2 HOWTO was thrown together with the help of Matt Welsh, Jeff Uphoff, and Alan Cox. Hopefully it will help someone out there get going with networking under Linux. Future plans for the NET-2 HOWTO include a section on setting up your own Linux LAN (with SLIP and/or Ethernet), adventures in routing, and the use of netstat and other network administration under Linux. For now, the information here should be more than enough. :) If you have questions about setting up NET-2, feel free to mail me, or if you have any corrections, additions, or errata for this NET-2 HOWTO, send me any and all changes (cdiffs are nice, but I'm flexible). Of course, thanks to Fred, Linus, Ross, Phil, Paul, Don, and everyone else who helped to develop the NET-2 code and work on previous versions of TCP/IP for Linux and the NET-FAQ. Finally, Linux has a complete implementation of TCP/IP. It may not be for everyone yet. But for those who want to do some hacking---here it is. Cheers, Terry Dawson, (terryd@extro.ucc.su.oz.au)