Part 4 of the Linux Newbie Administrator Guide
4.5.2 How to set up my home network?
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Hardware. Your hardware must be set up properly. Your network card should have been set up during the initial RedHat installation. If you added your card later, chances are it was autodetected and configured during a subsequent bootup (by kudzu). If it wasn't, you may want to set up your network card now. If you have more than one network card on your computer, you will also need to set up the second cards manually, since Linux will autodetect only 1 network card. Under Linux, most drivers for network cards are implemented as modules. So setting up a card manually involves just inserting the proper module with its parameters. You don't need to recompile the kernel, nor even reboot your computer (unless you have an uncommon card). To figure out what module(s) and parameters you need, you may want to consult the documentations that comes with the kernel source code: less /usr/src/linux-2.4/Documentation/networking/net-modules.txt If needed, you can list all the modules available for your kernel using something like: modprobe -l | more If you need more help, see the Linux Network Administrator Guide (file/usr/share/doc/LDP/nag on your system or check http://www.tldp.org/LDP/nag/). This excellent guide is known as nag. There are many ways of inserting a module into a kernel. For a network card, the simplest is to start, as root, netconf and specify the module name there. An alternative is to start an X-terminal, execute "su" (to make yourself a root) and then run /usr/bin/kernelcfg In most cases, you don't have to specify the parameters (IRQ and address) for your module--the module will know what they should be. However, the parameters were a problem during my setup of two network cards on one computer--you must make sure that you don't have any hardware conflicts. A common source of problems is that the card wants to configure on IRQ 5, which is occupied by the SoundBlaster, or IRQ 3 which conflicts with the second serial port (COM2, cua1, ttyS1). Inspecting the files /proc/interrupts, /proc/ioport and reading bootup messages may help. For example, my WD8013 card (same as SMC Elite and SMC Elite plus, according to nag) runs under IRQ 10 (set by a jumper on the card and I specified the IRQ in the kernel module setup), under the address 0x300 and uses the "WD" module. My "SMC EtherEZ" card (no jumper settings on the card) runs under IRQ 9, address 0x240 and uses "SMC EtherEZ" module. Please make sure you don't omit the leading "0x" in the address--it means "hexadecimal" and must be there else the number will be interpreted as decimal. After the module is inserted, you may want to inspect the file /proc/modules to see if the module is indeed loaded (or run lsmod as root). The module configuration file is /etc/modules.conf so if you encounter difficulties (for example, I had difficulty removing modules inserted by mistake), just edit and adjust this file manually, e.g., using pico. Network configuration. After setting up the network cards and connecting the cables, set up the network by running (as root): netconf This program
has help! netconf can also be run under GUI, but I did
not really try it. If you need more understanding of how networking works,
you may want to read the previously mentioned nag. Also, reading this
material may be of help: http://ieee.uow.edu.au/~mjp16/wylug-netlinux/notes.html.
How and what to fill up in netconf depends on your network. You surely want to fill up "Basic Host Information" (enable the first ethernet interface, eth0, fill in the name, aliases and IP number of your local computer) and the "Information About Other Hosts" (names, aliases and IPs of other computers on your home network). This information goes to the files: /etc/hosts and /etc/sysconfig/network, so you may want to inspect these files and adjust them manually. When setting up the network, don't mess up with the "loopback driver" which has the IP 127.0.0.1. It is always there--it is the IP through which the computer talks to itself. If you don't have an IP address (as will typically be the case for a home network with no permanent connection to the outside world), you may want to invent one. It does not matter very much what it is since when connecting to the outside world by your modem, you will be dynamically allocated an IP address (a machine can have many IP addresses at the same time). Your invented IP must be formally correct and the net mask must match the class of the network (class A, B or C). See the chapter on IP addresses in the already mentioned Network Administrator Guide (nag) (/usr/doc/LPD/nag on your system, or if you don't have it, download it now from http://metalab.unc.edu/mdw/index.html#guide. For a home network, you might want to invent a class C network (up to 254 machines, the smallest) IP number which has the first three digits between 192 to 223. The last three digits identify the machine on your class C network and must be between 1 and 254 (don't use 0, it means "whole network" or 255 which is the "broadcast address"). The middle two sets of digits can be anything from 0 to 255. Thus 223.223.223.1 is the first machine on the class C network 223.223.223.0 (the last zero signifies the whole network), with the broadcast address 223.223.223.255. The network mask for a class C network is always 255.255.255.0 (unless you subdivide your network into smaller "subnet", which is not discussed here). Rather than completely inventing an IP number, it might be safer/better to use one of the numbers reserved for "private networks". For me, the IP number 192.168.1.1 works just fine. This way, your "invented" IP address is guaranteed never to interfere with any IP that may exist in the world. Typically, the first machine on a network is the one that is expected to have the connection to the outside world (since it was connected first, but there is no standard for that). So, I filled up the GATEWAY to xxx.xxx.xxx.1 (my first machine) on all machines, except for the machine xxx.xxx.xxx.1, where I left this field blank. Actually, although I left the field blank, netconf inserted the gateway 0.0.0.0 into the /etc/sysconf file. This was a source of an annoying error message during the loading of the network card on the bootup. To get rid of the message, I edited /etc/sysconfig/network and set it to something like this: GATEWAYDEV=
[You don't want a gateway on your ethernet interface on this machine if it does not lead to the outside world. The ppp interface on this first machine will be set up as a default gateway once you connect through your modem, e.g. using kppp.] The name of a computer is entirely arbitrary--the main user normally chooses a short word s/he likes. The domain name of the home network is also entirely arbitrary, unless you have a permanent connection in which case a domain name is registered to you. Try to invent something that does not exist yet--it could make your life easier once you have a permanent connection. As for the DNS (domain name server, also called "named" = name daemon), RedHat 5.2 and 6.0 comes with DNS preinstalled as "caching-only" so it is easy to configure as such. You may also choose not to use local DNS at all--if your local DNS is looking up an "outside" server and can't find it, it can be a real show-stopper (the machine can appear to be hanged for up to a few minutes). To use local DNS, the "named" service must be enabled-- check this by running setup. To set up the caching-only DNS, fill up the appropriate boxes in netconf. E.g., I filled "nameserver 1" to my first machine on all computers (I entered the loopback address 127.0.0.1 on the machine xxx.xxx.xxx.1, and the proper xxx.xxx.xxx.1 address on all other machines). No routes to other networks and hosts were required in my network, since I don't have other local networks. So I left this field blank. Other than setting up the hardware correctly and filling up the info under netconf on each computer, as described above, I did not have to do anything on the standard RedHat to get my network working. Reboot all
computers one by one in any order (this is not necessary, but won't hurt
you) and watch the boot messages (if they scroll too fast off screen,
use telnet name_of_the_machine_you_are_sitting_at After a successful login, you can exit the telnet session by typing exit Finally, try to telnet another computer on your network: telnet name_of_a_remote_machine If this works on all machines, your eth0 network interface is set up. After setting up your ppp and connecting to your Internet Service Provider (ISP), you will have another network interface (ppp0) and then will be able to telnet any machine in the world. Next > 4.5.3 I have problems configuring my ppp dial out
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