143 lines
4.4 KiB
HTML
Executable File
143 lines
4.4 KiB
HTML
Executable File
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/REC-html40/strict.dtd">
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<!-- $Id: //BBN_Linux/Branch/Branch_for_Rel_TP_ASEAN_20161216/tclinux_phoenix/apps/public/radvd-1.5/INTRO.html#1 $ -->
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<html lang="en">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>RADVD Introduction</title>
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</head>
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<body>
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<h1>RADVD Introduction</h1>
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<p>
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by <a href="mailto:lf@elemental.net">Lars Fenneberg</a> et al. Updated
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2002-01-12.
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</p>
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<p>
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<a href="http://www.ietf.org/rfc/rfc2460.txt">IPv6</a> has a lot more
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support for autoconfiguration than
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<a href="http://www.ietf.org/rfc/rfc791.txt">IPv4</a>. But for this
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autoconfiguration to work on the hosts of a network, the <em>routers</em>
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of the local network have to run a program which answers the
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autoconfiguration requests of the hosts.
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</p>
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<p>
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On Linux this program is called
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<a href="http://v6web.litech.org/radvd/">radvd</a>, which stands for
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Router ADVertisement Daemon. This daemon listens to Router Solicitations
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(RS) and answers with Router Advertisement (RA). Furthermore unsolicited
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RAs are also send from time to time.
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<a href="http://www.ietf.org/rfc/rfc4861.txt">RFC 4861</a> defines most
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functions of radvd.
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</p>
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<p>
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Router Advertisements contain information, which is used by hosts to
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configure their interfaces. This information includes address prefixes,
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the MTU of the link and information about default routers.
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</p>
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<p>
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Of course the routers can't autoconfigure themselves, so the information
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on the routers has to be provided by the administrator of the system.
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This is done by manually configuring the interfaces and routes and by
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configuring the router advertisement daemon.
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</p>
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<p>
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A small and simple configuration file for radvd might look like this:
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</p>
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<p>
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<pre>
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interface eth0
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{
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AdvSendAdvert on;
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prefix 2001:db8:0:1::/64
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{
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AdvOnLink on;
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AdvAutonomous on;
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};
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};
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</pre>
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<p>
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It says that radvd should advertise (AdvSendAdvert on) the prefix
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2001:db8:0:1:: which has a lenght of 64 on the interface eth0.
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Also the prefix is marked as autonomous (AdvAutonomous on) and as on-link
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(AdvOnLink on). The both currently default to enabled but are included
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here for introductory purposes; it isn't necessary to define them.
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All the other options are left on their default values.
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</p>
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<p>
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Autonomous means that the prefix can be used for automatic address
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configuration and on-link means that the hosts can assume that all the hosts
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which use this prefix are reachable via the interface on which the host
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received this RA.
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</p>
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<p>
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The prefix must be 64 bits long (apart from very few exceptions), as dictated by
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<a href="http://www.ietf.org/rfc/rfc2464.txt">RFC 2464</a> and other
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standards for different link-layer technologies. For more
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details, see <a href="http://www.ietf.org/rfc/rfc4862.txt">RFC 4862</a>
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(IPv6 Stateless Address Autoconfiguration) and
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<a href="http://www.ietf.org/rfc/rfc2464.txt">RFC 2464</a>
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(Transmission of IPv6 Packets over Ethernet Networks). For more information
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on configuring radvd please look at the manual pages which are included in
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the radvd distribution.
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</p>
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<p>
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So, when an interface on a hosts is UPed and a RA is received, the host
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can configure an address on the interface by using the prefix and
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appending the EUI-64 identifier derived from the hardware address
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(also called link-layer token). The EUI-64 identifier is simply appended
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after the prefix. For example:
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</p>
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<p>
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<pre>
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Announced prefix: 2001:db8:0:1::
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MAC address: 00:07:E9:7B:02:59
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EUI-64 identifier: 0207:e9ff:fe7b:259
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Configured address: 2001:db8:0:1:207:e9ff:fe7b:259
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</pre>
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<p>
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The host can also choose a default router by examining the RA.
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the rest works automatically.
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</p>
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<p>
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So now we've configured radvd, but we still need to configure the interfaces
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and set the routes (on the router). There's a lot of good material on
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setting up IPv6, and the reader is encouraged to have a look
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at it; for example:
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</p>
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<p>
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<ul>
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<li><a href="http://www.bieringer.de/linux/IPv6/IPv6-HOWTO/IPv6-HOWTO.html">http://www.bieringer.de/linux/IPv6/IPv6-HOWTO/IPv6-HOWTO.html</a></li>
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<li><a href="http://people.debian.org/~csmall/ipv6/setup.html">http://people.debian.org/~csmall/ipv6/setup.html</a> (for non-Debian too)</li>
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</ul>
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<hr>
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<p>
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Copyright © 1997 <a href="mailto:lf@elemental.net">Lars Fenneberg</a>
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</p>
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</body>
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</html>
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