release/src/router/radvd/INTRO.html

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   6 <title>RADVD Introduction</title>
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  10 <h1>RADVD Introduction</h1>
  11
  12 <p>
  13 by <a href="mailto:lf@elemental.net">Lars Fenneberg</a> et al. Updated
  14 2002-01-12.
  15 </p>
  16
  17 <p>
  18 <a href="http://www.ietf.org/rfc/rfc2460.txt">IPv6</a> has a lot more
  19 support for autoconfiguration than
  20 <a href="http://www.ietf.org/rfc/rfc791.txt">IPv4</a>. But for this
  21 autoconfiguration to work on the hosts of a network, the <em>routers</em>
  22 of the local network have to run a program which answers the
  23 autoconfiguration requests of the hosts.
  24 </p>
  25
  26 <p>
  27 On Linux this program is called
  28 <a href="http://v6web.litech.org/radvd/">radvd</a>, which stands for
  29 Router ADVertisement Daemon. This daemon listens to Router Solicitations
  30 (RS) and answers with Router Advertisement (RA). Furthermore unsolicited
  31 RAs are also send from time to time.
  32 <a href="http://www.ietf.org/rfc/rfc4861.txt">RFC 4861</a> defines most
  33 functions of radvd.
  34 </p>
  35
  36 <p>
  37 Router Advertisements contain information, which is used by hosts to
  38 configure their interfaces. This information includes address prefixes,
  39 the MTU of the link and information about default routers.
  40 </p>
  41
  42 <p>
  43 Of course the routers can't autoconfigure themselves, so the information
  44 on the routers has to be provided by the administrator of the system.
  45 This is done by manually configuring the interfaces and routes and by
  46 configuring the router advertisement daemon.
  47 </p>
  48
  49 <p>
  50 A small and simple configuration file for radvd might look like this:
  51 </p>
  52
  53 <p>
  54 <pre>
  55
  56 interface eth0
  57 {
  58         AdvSendAdvert on;
  59         prefix 2001:db8:0:1::/64
  60         {
  61                 AdvOnLink on;
  62                 AdvAutonomous on;
  63         };
  64 };
  65
  66 </pre>
  67
  68 <p>
  69 It says that radvd should advertise (AdvSendAdvert on) the prefix
  70 2001:db8:0:1:: which has a lenght of 64 on the interface eth0.
  71 Also the prefix is marked as autonomous (AdvAutonomous on) and as on-link
  72 (AdvOnLink on). The both currently default to enabled but are included
  73 here for introductory purposes; it isn't necessary to define them.
  74 All the other options are left on their default values.
  75 </p>
  76
  77 <p>
  78 Autonomous means that the prefix can be used for automatic address
  79 configuration and on-link means that the hosts can assume that all the hosts
  80 which use this prefix are reachable via the interface on which the host
  81 received this RA.
  82 </p>
  83
  84 <p>
  85 The prefix must be 64 bits long (apart from very few exceptions), as dictated by
  86 <a href="http://www.ietf.org/rfc/rfc2464.txt">RFC 2464</a> and other
  87 standards for different link-layer technologies. For more
  88 details, see <a href="http://www.ietf.org/rfc/rfc4862.txt">RFC 4862</a>
  89 (IPv6 Stateless Address Autoconfiguration) and
  90 <a href="http://www.ietf.org/rfc/rfc2464.txt">RFC 2464</a>
  91 (Transmission of IPv6 Packets over Ethernet Networks). For more information
  92 on configuring radvd please look at the manual pages which are included in
  93 the radvd distribution.
  94 </p>
  95
  96 <p>
  97 So, when an interface on a hosts is UPed and a RA is received, the host
  98 can configure an address on the interface by using the prefix and
  99 appending the EUI-64 identifier derived from the hardware address
 100 (also called link-layer token). The EUI-64 identifier is simply appended
 101 after the prefix. For example:
 102 </p>
 103
 104 <p>
 105 <pre>
 106
 107    Announced prefix:    2001:db8:0:1::
 108
 109    MAC address:         00:07:E9:7B:02:59
 110
 111    EUI-64 identifier:   0207:e9ff:fe7b:259
 112
 113    Configured address:  2001:db8:0:1:207:e9ff:fe7b:259
 114
 115 </pre>
 116
 117 <p>
 118 The host can also choose a default router by examining the RA.
 119 the rest works automatically.
 120 </p>
 121
 122 <p>
 123 So now we've configured radvd, but we still need to configure the interfaces
 124 and set the routes (on the router).  There's a lot of good material on
 125 setting up IPv6, and the reader is encouraged to have a look
 126 at it; for example:
 127 </p>
 128
 129 <p>
 130 <ul>
 131 <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>
 132 <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>
 133 </ul>
 134
 135 <hr>
 136
 137 <p>
 138 Copyright &copy; 1997 <a href="mailto:lf@elemental.net">Lars Fenneberg</a>
 139 </p>
 140
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