45 lines
2.0 KiB
HTML
45 lines
2.0 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>Metric Values</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="node33.html">The Internet Control Message </A>
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<B>Up:</B> <A HREF="node27.html">IP Routing</A>
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<B> Previous:</B> <A HREF="node31.html">The Routing Table</A>
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<BR> <P>
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<H2><A NAME="SECTION004450000">Metric Values</A></H2>
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Dynamic routing based on RIP chooses the best route to some destination
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host or network based on the number of ``hops'', that is, the gateways a
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datagram has to pass before reaching it. The shorter a route is, the
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better RIP rates it. Very long routes with 16 or more hops are regarded
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as unusable, and are discarded.
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<P>
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To use RIP to manage routing information internal to your local
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network, you have to run gated on all hosts. At boot time,
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gated checks for all active network interfaces. If there is
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more than one active interface (not counting the loopback interface),
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it assumes the host is switching packets between several networks, and
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will actively exchange and broadcast routing information. Otherwise,
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it will only passively receive any RIP updates and update the local
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routing table.
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<P>
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When broadcasting the information from the local routing table,
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gated computes the length of the route from the so-called
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<em>metric value</em> associated with the routing table entry. This
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metric value is set by the system administrator when configuring the
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route and should reflect the actual cost of using this route. Therefore,
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the metric of a route to a subnet the host is directly connected to
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should always be zero, while a route going through two gateways should
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have a metric of two. However, note that you don't have to bother about
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metrics when you don't use RIP or gated.
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<HR>
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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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