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shorewall_code/docs/6to4.xml
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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
"http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd">
<article>
<!--$Id$-->
<articleinfo>
<title>6to4 Tunnels</title>
<authorgroup>
<author>
<firstname>Eric</firstname>
<surname>de Thouars</surname>
</author>
<author>
<firstname>Tom</firstname>
<surname>Eastep</surname>
</author>
</authorgroup>
<pubdate><?dbtimestamp format="Y/m/d"?></pubdate>
<copyright>
<year>2003-2004</year>
<holder>Eric de Thouars and Tom Eastep</holder>
</copyright>
<legalnotice>
<para>Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License, Version
1.2 or any later version published by the Free Software Foundation; with
no Invariant Sections, with no Front-Cover, and with no Back-Cover
Texts. A copy of the license is included in the section entitled
<quote><ulink url="GnuCopyright.htm">GNU Free Documentation
License</ulink></quote>.</para>
</legalnotice>
</articleinfo>
<warning>
<para>The 6to4 tunnel feature of Shorewall only facilitates IPv6 over IPv4
tunneling. It does not provide any IPv6 security measures.</para>
</warning>
<para>6to4 tunneling with Shorewall can be used to connect your IPv6 network
to another IPv6 network over an IPv4 infrastructure.</para>
<para>More information on Linux and IPv6 can be found in the <ulink
url="http://www.tldp.org/HOWTO/Linux+IPv6-HOWTO">Linux IPv6 HOWTO</ulink>.
Details on how to setup a 6to4 tunnels are described in the section <ulink
url="http://www.tldp.org/HOWTO/Linux+IPv6-HOWTO/configuring-ipv6to4-tunnels.html">Setup
of 6to4 tunnels</ulink>.</para>
<section id="Tunnel6to4">
<title>Connecting two IPv6 Networks</title>
<para>Suppose that we have the following situation:</para>
<graphic fileref="images/TwoIPv6Nets1.png" />
<para>We want systems in the 2002:100:333::/64 subnetwork to be able to
communicate with the systems in the 2002:488:999::/64 network. This is
accomplished through use of the <filename>/etc/shorewall/tunnels</filename>
file and the <quote>ip</quote> utility for network interface and routing
configuration.</para>
<para>Unlike GRE and IPIP tunneling, the
<filename>/etc/shorewall/policy</filename>,
<filename>/etc/shorewall/interfaces</filename> and
<filename>/etc/shorewall/zones</filename> files are not used. There is no
need to declare a zone to represent the remote IPv6 network. This remote
network is not visible on IPv4 interfaces and to iptables. All that is
visible on the IPv4 level is an IPv4 stream which contains IPv6 traffic.
Separate IPv6 interfaces and ip6tables rules need to be defined to handle
this traffic.</para>
<para>In <filename>/etc/shorewall/tunnels</filename> on system A, we need
the following:</para>
<programlisting>#TYPE ZONE GATEWAY GATEWAY ZONE
6to4 net 134.28.54.2</programlisting>
<para>This entry in <filename>/etc/shorewall/tunnels</filename> opens the
firewall so that the IPv6 encapsulation protocol (41) will be accepted
to/from the remote gateway.</para>
<para>Use the following commands to setup system A:</para>
<programlisting>&gt;<command>ip tunnel add tun6to4 mode sit ttl 254 remote 134.28.54.2</command>
&gt;<command>ip link set dev tun6to4 up</command>
&gt;<command>ip addr add 3ffe:8280:0:2001::1/64 dev tun6to4</command>
&gt;<command>ip route add 2002:488:999::/64 via 3ffe:8280:0:2001::2</command></programlisting>
<para>Similarly, in <filename>/etc/shorewall/tunnels</filename> on system
B we have:</para>
<programlisting>#TYPE ZONE GATEWAY GATEWAY ZONE
6to4 net 206.191.148.9</programlisting>
<para>And use the following commands to setup system B:</para>
<programlisting>&gt;<command>ip tunnel add tun6to4 mode sit ttl 254 remote 206.191.148.9</command>
&gt;<command>ip link set dev tun6to4 up</command>
&gt;<command>ip addr add 3ffe:8280:0:2001::2/64 dev tun6to4</command>
&gt;<command>ip route add 2002:100:333::/64 via 3ffe:8280:0:2001::1</command></programlisting>
<para>On both systems, restart Shorewall and issue the configuration
commands as listed above. The systems in both IPv6 subnetworks can now
talk to each other using IPv6.</para>
</section>
</article>