80 lines
4.3 KiB
HTML
80 lines
4.3 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
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<!--Converted with LaTeX2HTML 96.1-c (Feb 29, 1996) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds -->
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<HTML>
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<HEAD>
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<TITLE>Assigning IP-Addresses</TITLE>
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</HEAD>
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<BODY LANG="EN">
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<A HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="contents_motif.gif"></A> <BR>
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<B> Next:</B> <A HREF="node64.html">Writing hosts and networks </A>
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<B>Up:</B> <A HREF="node58.html">Configuring TCP/IP Networking</A>
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<B> Previous:</B> <A HREF="node62.html">Setting the Hostname</A>
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<BR> <P>
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<H1><A NAME="SECTION007500000">Assigning IP-Addresses</A></H1>
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If you configure the networking software on your host for standalone
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operation (for instance, to be able to run the INN netnews software),
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you can safely skip this section, because you will need an IP-address
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just for the loopback interface, which is always 127.0.0.1.
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<P>
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Things are a little more complicated with real networks like Ethernets.
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If you want to connect your host to an existing network, you have to ask
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its administrators to give you an IP-address on this network. When
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setting up the network all by yourself, you have to assign IP-addresses
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yourself as described below.
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<P>
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Hosts within a local network should usually share addresses from the
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same logical IP-network. Hence you have to assign an IP-network address.
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If you have several physical networks, you either have to assign them
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different network numbers, or use sub-netting to split your IP-address
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range into several subnetworks.
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<P>
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If your network is not connected to the Internet, you are free to choose
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any (legal) network address. You only have to make sure to choose one from
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classes A, B, or C, else things will most likely not work properly.
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However, if you intend to get on the Internet in the near future, you
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should obtain an official IP-address <em>now</em>. The best way to proceed is
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to ask your network service provider to help you. If you want to obtain a
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network number just in case you might get on the Internet someday, request
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a Network Address Application Form from hostmaster@internic.net.
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<p>
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To operate several Ethernets (or other networks, once a driver is
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available), you have to split your network into subnets. Note that
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sub-netting is required only if you have more than one <em>broadcast
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network</em>; point-to-point links don't count. For instance, if you have
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one Ethernet, and one or more SLIP links to the outside world, you
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don't need to subnet your network. The reason for this will be
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explained in chapter-<A HREF="node92.html#slip"><IMG ALIGN=BOTTOM ALT="gif" SRC="cross_ref_motif.gif"></A>.
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<P>
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As an example, the brewery's network manager applies to the NIC for a
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class B network number, and is given 191.72.0.0. To accommodate
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the two Ethernets, she decides to use eight bits of the host part as
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additional subnet bits. This leaves another eight bits for the host
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part, allowing for 254 hosts on each of the subnets. She then assigns
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subnet number 1 to the brewery, and gives the winery number 2. Their
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respective network addresses are thus 191.72.1.0 and
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191.72.2.0. The subnet mask is 255.255.255.0.
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<P>
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vlager, which is the gateway between the two networks, is assigned a
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host number of 1 on both of them, which gives it the IP-addresses
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191.72.1.1 and 191.72.2.1, respectively.
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Figure-<A HREF="node64.html#interfacefigsubnet"><IMG ALIGN=BOTTOM ALT="gif" SRC="cross_ref_motif.gif"></A> shows the two subnets, and the gateway.
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<P>
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Note that in this example I am using a class B network to keep things
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simple; a class C network would be more realistic. With the new networking
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code, sub-netting is not limited to byte boundaries, so even a class C
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network may be split into several subnets. For instance, you could use 2
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bits of the host part for the netmask, giving you four possible subnets
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with 64 hosts on each.<A HREF="footnode.html#2589"><IMG ALIGN=BOTTOM ALT="gif" SRC="foot_motif.gif"></A>
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<P>
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<HR><A HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="contents_motif.gif"></A> <BR>
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<B> Next:</B> <A HREF="node64.html">Writing hosts and networks </A>
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<B>Up:</B> <A HREF="node58.html">Configuring TCP/IP Networking</A>
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<B> Previous:</B> <A HREF="node62.html">Setting the Hostname</A>
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<P><ADDRESS>
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<I>Andrew Anderson <BR>
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Thu Mar 7 23:22:06 EST 1996</I>
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</ADDRESS>
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</BODY>
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</HTML>
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