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568 lines
21 KiB
XML
568 lines
21 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
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"http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd">
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<article>
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<!--$Id$-->
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<articleinfo>
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<title>6to4 Tunnels</title>
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<authorgroup>
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<author>
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<firstname>Eric</firstname>
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<surname>de Thouars</surname>
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</author>
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<author>
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<firstname>Tom</firstname>
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<surname>Eastep</surname>
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</author>
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</authorgroup>
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<pubdate><?dbtimestamp format="Y/m/d"?></pubdate>
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<copyright>
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<year>2003-2004</year>
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<year>2008</year>
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<year>2009</year>
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<holder>Eric de Thouars and Tom Eastep</holder>
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</copyright>
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<legalnotice>
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<para>Permission is granted to copy, distribute and/or modify this
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document under the terms of the GNU Free Documentation License, Version
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1.2 or any later version published by the Free Software Foundation; with
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no Invariant Sections, with no Front-Cover, and with no Back-Cover
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Texts. A copy of the license is included in the section entitled
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<quote><ulink url="GnuCopyright.htm">GNU Free Documentation
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License</ulink></quote>.</para>
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</legalnotice>
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</articleinfo>
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<para>6to4 tunneling with Shorewall can be used to connect your IPv6 network
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to another IPv6 network over an IPv4 infrastructure. It can also allow you
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to experiment with IPv6 even if your ISP doesn't provide IPv6
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connectivity.</para>
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<para>More information on Linux and IPv6 can be found in the <ulink
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url="http://www.tldp.org/HOWTO/Linux+IPv6-HOWTO">Linux IPv6 HOWTO</ulink>.
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Details on how to setup a 6to4 tunnels are described in the section <ulink
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url="http://www.tldp.org/HOWTO/Linux+IPv6-HOWTO/configuring-ipv6to4-tunnels.html">Setup
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of 6to4 tunnels</ulink>.</para>
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<section id="FeetWet">
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<title>Getting your Feet Wet with IPv6, by Tom Eastep</title>
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<para>6to4 tunnels provide a good way to introduce yourself to IPv6.
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<ulink url="IPv6Support.html">Shorewall6</ulink> was developed on a
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network whose only IPv6 connectivity was an 6to4 Tunnel; that network is
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described in the remainder of this section. What is shown here requires
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Shorewall6 4.2.4 or later.</para>
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<section>
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<title>Configuring IPv6 using my script</title>
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<para>I have created an init <ulink
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url="/pub/shorewall/contrib/IPv6/ipv6">script</ulink> to make the job of
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configuring your firewall for IPv6 easier.</para>
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<para>The script is installed in /etc/init.d and configures ipv6,
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including a 6to4 tunnel, at boot time. Note that the script is included
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in the Shorewall6 distribution but is not installed in /etc/init.d by
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default. The RPMs from shorewall.net, install the file in the package
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documentation directory.</para>
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<para>The script works on OpenSuSE 11.0 and may need modification for
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other distributions. On OpenSuSE, the script is installed by copying it
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to <filename>/etc/init.d/</filename> then running the command 'chkconfig
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--add ipv6'.</para>
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<para>At the top of the script, you will see several variables:</para>
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<itemizedlist>
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<listitem>
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<para>SIT - The name of the tunnel device. Usually 'sit1'</para>
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</listitem>
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<listitem>
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<para>INTERFACES - local interfaces that you want to configure for
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IPv6</para>
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</listitem>
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<listitem>
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<para>ADDRESS4 - A static IPv4 address on your firewall that you
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want to use for the tunnel.</para>
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</listitem>
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<listitem>
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<para>SLA - The identity of the first local sub-network that you
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want to assign to the interfaces listed in INTERFACES. Normally one
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(0001).</para>
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</listitem>
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<listitem>
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<para>GATEWAY - The default IPv6 gateway. For 6to4, this is
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::192.88.99.1.</para>
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</listitem>
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</itemizedlist>
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<para>Here is the file from my firewall:</para>
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<blockquote>
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<para><programlisting>SIT="sit1"
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ADDRESS4=206.124.146.180
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INTERFACES="eth2 eth4"
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SLA=1
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GATEWAY=::192.88.99.1</programlisting></para>
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</blockquote>
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<para>eth2 is the interface to my local network (both wired and
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wireless). eth4 goes to my DMZ which holds a single server. Here is a
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diagram of the IPv4 network:</para>
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<graphic align="center" fileref="images/Network2009.png" />
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<para>Here is the configuration after IPv6 is configured; the part in
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bold font is configured by the /etc/init.d/ipv6 script.</para>
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<blockquote>
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<para><programlisting>gateway:~ # ip -6 addr ls
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1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436
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inet6 ::1/128 scope host
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valid_lft forever preferred_lft forever
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2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
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<emphasis role="bold"> inet6 2002:ce7c:92b4:1::1/64 scope global
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valid_lft forever preferred_lft forever</emphasis>
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inet6 fe80::202:e3ff:fe08:55fa/64 scope link
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valid_lft forever preferred_lft forever
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3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
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inet6 fe80::202:e3ff:fe08:484c/64 scope link
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valid_lft forever preferred_lft forever
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4: eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
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<emphasis role="bold"> inet6 2002:ce7c:92b4:2::1/64 scope global
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valid_lft forever preferred_lft forever</emphasis>
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inet6 fe80::2a0:ccff:fed2:353a/64 scope link
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valid_lft forever preferred_lft forever
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24: sit1@NONE: <NOARP,UP,LOWER_UP> mtu 1480
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<emphasis role="bold"> inet6 ::206.124.146.180/128 scope global
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valid_lft forever preferred_lft forever
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inet6 2002:ce7c:92b4::1/128 scope global
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valid_lft forever preferred_lft forever</emphasis>
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gateway:~ # ip -6 route ls
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<emphasis role="bold">::/96 via :: dev sit1 metric 256 expires 21333315sec mtu 1480 advmss 1420 hoplimit 4294967295</emphasis>
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<emphasis role="bold">2002:ce7c:92b4::1 dev sit1 metric 256 expires 21333315sec mtu 1480 advmss 1420 hoplimit 4294967295
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2002:ce7c:92b4:1::/64 dev eth0 metric 256 expires 21333315sec mtu 1500 advmss 1440 hoplimit 4294967295
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2002:ce7c:92b4:2::/64 dev eth2 metric 256 expires 21333315sec mtu 1500 advmss 1440 hoplimit 4294967295</emphasis>
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fe80::/64 dev eth0 metric 256 expires 20748424sec mtu 1500 advmss 1440 hoplimit 4294967295
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fe80::/64 dev eth1 metric 256 expires 20748431sec mtu 1500 advmss 1440 hoplimit 4294967295
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fe80::/64 dev eth2 metric 256 expires 20748431sec mtu 1500 advmss 1440 hoplimit 4294967295
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fe80::/64 dev sit1 metric 256 expires 21333315sec mtu 1480 advmss 1420 hoplimit 4294967295
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<emphasis role="bold">default via ::192.88.99.1 dev sit1 metric 1 expires 21333315sec mtu 1480 advmss 1420 hoplimit 4294967295</emphasis>
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gateway:~ # </programlisting></para>
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</blockquote>
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<para>You will notice that sit1, eth0 and eth2 each have an IPv6 address
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beginning with 2002: -- All 6to4 IPv6 addresses have that in their most
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significant 16 bits. The next 32-bits (ce7c:92b4) encode the IPv4
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ADDRESS (206.124.146.180). So once you start the 6to4 tunnel, you are
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the proud owner of 2<superscript>80</superscript> IPv6 addresses! In the
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case shown here, 2002:ce7c:92b4::/48. The SLA is used to assign each
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interface in INTERFACES, a subnet of 2<superscript>64</superscript>
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addresses; in the case of eth0, 2002:ce7c:92b4:1::/64.</para>
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<para>I run <ulink url="http://www.litech.org/radvd/">radvd</ulink> on
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the firewall to allow hosts conntected to eth2 and eth4 to automatically
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perform their own IPv6 configuration. Here is my
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<filename>/etc/radvd.conf</filename> file:</para>
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<blockquote>
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<para><programlisting>interface eth2 {
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AdvSendAdvert on;
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MinRtrAdvInterval 3;
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MaxRtrAdvInterval 10;
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prefix 2002:ce7c:92b4:1::/64 {
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AdvOnLink on;
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AdvAutonomous on;
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AdvRouterAddr off;
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};
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RDNSS 2002:ce7c:92b4:2:2a0:ccff:fedb:31c4 {
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AdvRDNSSOpen on;
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AdvRDNSSPreference 2;
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};
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};
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interface eth4 {
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AdvSendAdvert on;
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MinRtrAdvInterval 3;
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MaxRtrAdvInterval 10;
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prefix 2002:ce7c:92b4:2::/64 {
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AdvOnLink on;
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AdvAutonomous on;
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AdvRouterAddr off;
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};
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RDNSS 2002:ce7c:92b4:2:2a0:ccff:fedb:31c4 {
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AdvRDNSSOpen on;
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AdvRDNSSPreference 2;
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};
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};</programlisting></para>
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</blockquote>
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<note>
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<para>radvd terminates immediately if IPv6 forwarding is not enabled.
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So it is a good idea to include this in<filename>
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/etc/sysctl.conf</filename>:</para>
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<programlisting>net.ipv6.conf.all.forwarding = 1</programlisting>
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<para>That way, if radvd starts before Shorewall6, it will continue to
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run.</para>
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<para>An alternative is to modify
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<filename>/etc/init.d/radvd</filename> so that radvd starts after
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Shorewall6:</para>
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<programlisting># Should-Start: shorewall6</programlisting>
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</note>
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<para>Here is the automatic IPv6 configuration on my server attached to
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eth2:</para>
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<blockquote>
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<para><programlisting>webadmin@lists:~/ftpsite/contrib/IPv6> /sbin/ip -6 addr ls
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1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436
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inet6 ::1/128 scope host
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valid_lft forever preferred_lft forever
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2: eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
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<emphasis role="bold"> inet6 2002:ce7c:92b4:2:2a0:ccff:fedb:31c4/64 scope global dynamic
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valid_lft 2591995sec preferred_lft 604795sec</emphasis>
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inet6 fe80::2a0:ccff:fedb:31c4/64 scope link
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valid_lft forever preferred_lft forever
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webadmin@lists:~/ftpsite/contrib/IPv6> /sbin/ip -6 route ls
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<emphasis role="bold">2002:ce7c:92b4:2::/64 dev eth2 proto kernel metric 256 expires 2592161sec mtu 1500 advmss 1440 hoplimit 4294967295</emphasis>
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fe80::/64 dev eth2 metric 256 expires 20746963sec mtu 1500 advmss 1440 hoplimit 4294967295
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fe80::/64 dev ifb0 metric 256 expires 20746985sec mtu 1500 advmss 1440 hoplimit 4294967295
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<emphasis role="bold">default via fe80::2a0:ccff:fed2:353a dev eth2 proto kernel metric 1024 expires 29sec mtu 1500 advmss 1440 hoplimit 64</emphasis>
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webadmin@lists:~/ftpsite/contrib/IPv6> </programlisting></para>
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</blockquote>
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<para>You will note that the public IPv6 address of eth2
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(2002:ce7c:92b4:2:2a0:ccff:fedb:31c4) was formed by concatenating the
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prefix for eth2 shown in radvd.conf (2002:ce7c:92b4:2) and the lower 64
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bits of the link level address of eth2 (2a0:ccff:fedb:31c4). You will
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also notice that the address 2002:ce7c:92b4:2:2a0:ccff:fedb:31c4 appears
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in the RDNSS clauses in radvd.conf; that causes my server to be
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automatically configured as a DNS server.</para>
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<para>The default route is described using the link level address of
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eth2 on the firewall (fe80::2a0:ccff:fed2:353a).</para>
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<para>On my laptop, ursa:</para>
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<blockquote>
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<para><programlisting>ursa:~ # ip -6 addr ls dev eth0
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3: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
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<emphasis role="bold"> inet6 2002:ce7c:92b4:1:21a:24ff:fecb:2bcc/64 scope global dynamic
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valid_lft 2591996sec preferred_lft 604796sec</emphasis>
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inet6 fe80::21a:73ff:fedb:8c35/64 scope link
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valid_lft forever preferred_lft forever
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ursa:~ # ip -6 route ls dev eth0
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<emphasis role="bold">2002:ce7c:92b4:1::/64 proto kernel metric 256 expires 2592160sec mtu 1500 advmss 1440 hoplimit 4294967295</emphasis>
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fe80::/64 metric 256 expires 21314573sec mtu 1500 advmss 1440 hoplimit 4294967295
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<emphasis role="bold">default via fe80::202:e3ff:fe08:55fa proto kernel metric 1024 expires 28sec mtu 1500 advmss 1440 hoplimit 64</emphasis>
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ursa:~ #</programlisting></para>
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</blockquote>
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<para>Here is the resulting simple IPv6 Network:</para>
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<graphic align="center" fileref="images/Network2008c.png" />
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</section>
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<section>
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<title>Configuring IPv6 the Debian Way</title>
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<para>In May 2009, I rebuilt the above firewall using Debian GNU/Linux
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and decided to configure IPv6 using the
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<filename>/etc/network/interfaces</filename> file.</para>
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<para>When I installed Debian Lenny on the system, the network
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interfaces were reunmbered as follows:</para>
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<table frame="void">
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<title>Interface Renaming</title>
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<tgroup cols="2">
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<tbody>
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<row>
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<entry><emphasis role="bold">Old
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Configuration</emphasis></entry>
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<entry><emphasis role="bold">New
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Configuration</emphasis></entry>
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</row>
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<row>
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<entry>eth0 (Avvanta Interface)</entry>
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<entry>eth3</entry>
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</row>
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<row>
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<entry>eth3 (Comcast Interface)</entry>
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<entry>eth0</entry>
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</row>
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<row>
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<entry>eth2 (Local Interface)</entry>
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<entry>eth1</entry>
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</row>
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<row>
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<entry>eth4 (DMZ Interface)</entry>
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<entry>eth2</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<para>So the IPv4 network was transformed to this:</para>
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<graphic align="center" fileref="images/Network2009a.png" />
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<para>To implement the same IPv6 network as described above, I used this
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/etc/shorewall/interfaces file:</para>
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<blockquote>
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<para><programlisting>auto lo
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iface lo inet loopback
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auto eth0
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iface eth0 inet dhcp
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hwaddress ether 00:11:85:89:da:9b
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auto eth1
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iface eth1 inet static
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address 172.20.1.254
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netmask 255.255.255.0
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network 172.20.1.0
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broadcast 172.20.1.255
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<emphasis role="bold">iface eth1 inet6 static
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address 2002:ce7c:92b4:1::1
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netmask 64 </emphasis>
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auto eth2
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iface eth2 inet static
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address 206.124.146.176
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netmask 255.255.255.255
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up ip route add 206.124.146.177/32 dev eth2
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<emphasis role="bold">iface eth2 inet6 static
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address 2002:ce7c:92b4:2::1
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netmask 64
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</emphasis>
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auto eth3 eth3:0 eth3:1 eth3:2
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iface eth3 inet static
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address 206.124.146.176
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netmask 255.255.255.0
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network 206.124.146.0
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broadcast 206.124.146.255
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iface eth3:0 inet static
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address 206.124.146.178
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netmask 255.255.255.0
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broadcast 206.124.146.255
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iface eth3:1 inet static
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address 206.124.146.179
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netmask 255.255.255.0
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broadcast 206.124.146.255
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iface eth3:2 inet static
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address 206.124.146.180
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netmask 255.255.255.0
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broadcast 206.124.146.255
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<emphasis role="bold">auto sit1
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iface sit1 inet6 v4tunnel
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address 2002:ce7c:92b4::1
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netmask 64
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endpoint 192.88.99.1
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local 206.124.146.180
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gateway ::192.88.99.1
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post-up echo 1 > /proc/sys/net/ipv6/conf/all/forwarding</emphasis></programlisting></para>
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</blockquote>
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<para>That file produces the following IPv6 network.</para>
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<graphic align="center" fileref="images/Network2009b.png" />
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</section>
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<section>
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<title>Configuring Shorewall</title>
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<para>We need to add an entry in /etc/shorewall/tunnels and restart
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Shorewall:</para>
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<blockquote>
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<para><programlisting>#TYPE ZONE GATEWAY GATEWAY
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# ZONE
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6to4 net
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#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
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</programlisting></para>
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</blockquote>
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</section>
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<section>
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<title>Configuring Shorewall6</title>
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<para><emphasis role="bold">STOP</emphasis> -- If you have followed the
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instructions above, you should have a completely functional IPv6
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network. Try:</para>
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<programlisting><emphasis role="bold">ping6 www.kame.net
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ping6 ipv6.chat.eu.freenode.net</emphasis>
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</programlisting>
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<para>If neither of those work from your firewall and from any local
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IPv6 systems that you have behind your firewall, do not go any further
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until one of them does work. If you ask for help from the Shorewall
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team, the first question we will ask is 'With Shorewall6 cleared, can
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you ping6 kame or freenode?'.</para>
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<para>The Shorewall6 configuration on my firewall is a very basic
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three-interface one.</para>
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<para>Key entry in
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<filename>/etc/shorewall6/shorewall6.conf</filename>:</para>
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<blockquote>
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<para><programlisting>IP_FORWARDING=On</programlisting></para>
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</blockquote>
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<para><filename>/etc/shorewall6/zones</filename>:</para>
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<blockquote>
|
|
<para><programlisting>#ZONE TYPE OPTIONS IN OUT
|
|
# OPTIONS OPTIONS
|
|
fw firewall
|
|
net ipv6
|
|
loc ipv6
|
|
dmz ipv6
|
|
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE</programlisting></para>
|
|
</blockquote>
|
|
|
|
<para><filename>/etc/shorewall6/interfaces</filename>:</para>
|
|
|
|
<blockquote>
|
|
<para><programlisting>#ZONE INTERFACE BROADCAST OPTIONS
|
|
net sit1 detect tcpflags,forward=1,nosmurfs
|
|
loc eth0 detect tcpflags,forward=1
|
|
dmz eth2 detect tcpflags,forward=1
|
|
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
|
|
</programlisting></para>
|
|
</blockquote>
|
|
|
|
<para><filename>/etc/shorewall6/policy</filename>:</para>
|
|
|
|
<blockquote>
|
|
<para><programlisting>#SOURCE DEST POLICY LOG LEVEL LIMIT:BURST
|
|
net all DROP info
|
|
loc net ACCEPT
|
|
dmz net ACCEPT
|
|
all all REJECT info</programlisting></para>
|
|
</blockquote>
|
|
|
|
<para><filename>/etc/shorewall6/rules</filename>:</para>
|
|
|
|
<blockquote>
|
|
<para><programlisting>#ACTION SOURCE DEST PROTO DEST SOURCE ORIGINAL RATE USER/ MARK
|
|
# PORT PORT(S) DEST LIMIT GROUP
|
|
#
|
|
# Accept DNS connections from the firewall to the network
|
|
#
|
|
DNS(ACCEPT) $FW net
|
|
#
|
|
# Accept SSH connections from the local network for administration
|
|
#
|
|
SSH(ACCEPT) loc $FW
|
|
#
|
|
# Allow Ping everywhere
|
|
#
|
|
Ping(ACCEPT) all all
|
|
|
|
#
|
|
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
|
|
</programlisting></para>
|
|
</blockquote>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="Tunnel6to4">
|
|
<title>Connecting two IPv6 Networks, by Eric de Thouars</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>><command>ip tunnel add tun6to4 mode sit ttl 254 remote 134.28.54.2</command>
|
|
><command>ip link set dev tun6to4 up</command>
|
|
><command>ip addr add 3ffe:8280:0:2001::1/64 dev tun6to4</command>
|
|
><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>><command>ip tunnel add tun6to4 mode sit ttl 254 remote 206.191.148.9</command>
|
|
><command>ip link set dev tun6to4 up</command>
|
|
><command>ip addr add 3ffe:8280:0:2001::2/64 dev tun6to4</command>
|
|
><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>
|