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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<article id="Multiple_Zones">
<articleinfo>
<title>Multiple Zones per Interface</title>
<authorgroup>
<author>
<firstname>Tom</firstname>
<surname>Eastep</surname>
</author>
</authorgroup>
<pubdate>2003-11-21</pubdate>
<copyright>
<year>2003</year>
<holder>Thomas M. 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 &#34;<ulink
url="GnuCopyright.htm">GNU Free Documentation License</ulink>&#34;.</para>
</legalnotice>
</articleinfo>
<section>
<title>Introduction</title>
<para>While most configurations can be handled with each of the
firewall&#39;s network interfaces assigned to a single zone, there are
cases where you will want to divide the hosts accessed through an
interface between two or more zones.</para>
<itemizedlist>
<listitem>
<para>The interface has multiple addresses on multiple subnetworks.
This case is covered in the <ulink
url="Shorewall_and_Aliased_Interfaces.html">Aliased Interface
documentation</ulink>.</para>
</listitem>
<listitem>
<para>You are using some form of NAT and want to access a server by
its external IP address from the same LAN segment. This is covered in
<ulink url="FAQ.htm#faq2">FAQs 2 and 2a</ulink>.</para>
</listitem>
<listitem>
<para>There are routers accessible through the interface and you want
to treat the networks accessed through that router as a separate zone.</para>
</listitem>
<listitem>
<para>Some of the hosts accessed through an interface have
significantly different firewalling requirements from the others so
you want to assign them to a different zone.</para>
</listitem>
</itemizedlist>
<para>The key points to keep in mind when setting up multiple zones per
interface are:</para>
<itemizedlist>
<listitem>
<para>Shorewall generates rules for zones in the order that the zone
declarations appear in /etc/shorewall/zones.</para>
</listitem>
<listitem>
<para>The order of entries in /etc/shorewall/hosts is immaterial as
far as the generated ruleset is concerned.</para>
</listitem>
</itemizedlist>
<para><emphasis role="bold">These examples use the local zone but the same
technique works for any zone.</emphasis> Remember that Shorewall
doesn&#39;t have any conceptual knowledge of &#34;Internet&#34;,
&#34;Local&#34;, or &#34;DMZ&#34; so all zones except the firewall itself
($FW) are the same as far as Shorewall is concerned. Also, the examples
use private (RFC 1918) addresses but public IP addresses can be used in
exactly the same way.</para>
</section>
<section>
<title>Router in the Local Zone</title>
<para>Here is an example of a router in the local zone.</para>
<note>
<para> the <emphasis role="bold">box called &#34;Router&#34; could be a
VPN server</emphasis> or other such device; from the point of view of
this discussion, it makes no difference.</para>
</note>
<graphic fileref="images/MultiZone1.png" />
<section>
<title>Can You Use the Standard Configuration?</title>
<para>In many cases, the <ulink url="two-interface.htm">standard
two-interface Shorewall setup</ulink> will work fine in this
configuration. It will work if:</para>
<itemizedlist>
<listitem>
<para>The firewall requirements to/from the internet are the same
for 192.168.1.0/24 and 192.168.2.0/24.</para>
</listitem>
<listitem>
<para>The hosts in 192.168.1.0/24 know that the route to
192.168.2.0/24 is through the <emphasis role="bold">router</emphasis>.</para>
</listitem>
</itemizedlist>
<para>All you have to do on the firewall is add a route to
192.168.2.0/24 through the <emphasis role="bold">router</emphasis> and
restart Shorewall.</para>
</section>
<section>
<title>Will One Zone be Enough?</title>
<para>If the firewalling requirements for the two local networks is the
same but the hosts in 192.168.1.0/24 don&#39;t know how to route to
192.168.2.0/24 then you need to configure the firewall slightly
differently. This type of configuration is rather stupid from an IP
networking point of view but it is sometimes necessary because you
simply don&#39;t want to have to reconfigure all of the hosts in
192.168.1.0/24 to add a persistent route to 192.168.2.0/24. On the
firewall:</para>
<orderedlist>
<listitem>
<para>Add a route to 192.168.2.0/24 through the <emphasis
role="bold">Router</emphasis>.</para>
</listitem>
<listitem>
<para>Set the &#39;routeback&#39; and &#39;newnotsyn&#39; options
for eth1 (the local firewall interface) in
/etc/shorewall/interfaces.</para>
</listitem>
<listitem>
<para>Restart Shorewall.</para>
</listitem>
</orderedlist>
</section>
<section>
<title>I Need Separate Zones</title>
<para>If you need to make 192.168.2.0/24 into it&#39;s own zone, you can
do it one of two ways; Nested Zones or Parallel Zones.</para>
<section>
<title>Nested Zones</title>
<para>You can define one zone (called it &#39;loc&#39;) as being all
hosts connectied to eth1 and a second zone &#39;loc1&#39;
(192.168.2.0/24) as a sub-zone.</para>
<graphic fileref="images/MultiZone1A.png" />
<para>The advantage of this approach is that the zone &#39;loc1&#39;
can use CONTINUE policies such that if a connection request
doesn&#39;t match a &#39;loc1&#39; rule, it will be matched against
the &#39;loc&#39; rules. For example, if your loc1-&#62;net policy is
CONTINUE then if a connection request from loc1 to the internet
doesn&#39;t match any rules for loc1-&#62;net then it will be checked
against the loc-&#62;net rules.</para>
<table>
<title>/etc/shorewall/zones</title>
<tgroup cols="3">
<thead>
<row>
<entry align="center">ZONE</entry>
<entry align="center">DISPLAY</entry>
<entry align="center">COMMENTS</entry>
</row>
</thead>
<tbody>
<row>
<entry>loc1</entry>
<entry>Local2</entry>
<entry>Hosts access through internal router</entry>
</row>
<row>
<entry>loc</entry>
<entry>Local</entry>
<entry>All hosts accessed via eth1</entry>
</row>
</tbody>
</tgroup>
</table>
<note>
<para>the sub-zone (loc1) is defined first!</para>
</note>
<table>
<title>/etc/shorewall/interfaces</title>
<tgroup cols="4">
<thead>
<row>
<entry align="center">ZONE</entry>
<entry align="center">INTERFACE</entry>
<entry align="center">BROADCAST</entry>
<entry align="center">OPTIONS</entry>
</row>
</thead>
<tbody>
<row>
<entry>loc</entry>
<entry>eth1</entry>
<entry>192.168.1.255</entry>
<entry>...</entry>
</row>
</tbody>
</tgroup>
</table>
<table>
<title>/etc/shorewall/hosts</title>
<tgroup cols="3">
<thead>
<row>
<entry align="center">ZONE</entry>
<entry align="center">HOSTS</entry>
<entry align="center">OPTIONS</entry>
</row>
</thead>
<tbody>
<row>
<entry>loc1</entry>
<entry>eth1:192.168.2.0/24</entry>
<entry></entry>
</row>
</tbody>
</tgroup>
</table>
<para>If you don&#39;t need Shorewall to set up infrastructure to
route traffic between &#39;loc&#39; and &#39;loc1&#39;, add these two
policies:</para>
<table>
<title>/etc/shorewall/policy</title>
<tgroup cols="5">
<thead>
<row>
<entry align="center">SOURCE</entry>
<entry align="center">DEST</entry>
<entry align="center">POLICY</entry>
<entry align="center">LOG LEVEL</entry>
<entry align="center">RATE:BURST</entry>
</row>
</thead>
<tbody>
<row>
<entry>loc</entry>
<entry>loc1</entry>
<entry>NONE</entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry>loc1</entry>
<entry>loc</entry>
<entry>NONE</entry>
<entry></entry>
<entry></entry>
</row>
</tbody>
</tgroup>
</table>
</section>
<section>
<title>Parallel Zones</title>
<para>You define both zones in the /etc/shorewall/hosts file to create
two disjoint zones.</para>
<graphic fileref="images/MultiZone1B.png" />
<table>
<title>/etc/shorewall/zones</title>
<tgroup cols="3">
<thead>
<row>
<entry align="center">ZONE</entry>
<entry align="center">DISPLAY</entry>
<entry align="center">COMMENTS</entry>
</row>
</thead>
<tbody>
<row>
<entry>loc1</entry>
<entry>Local1</entry>
<entry>Hosts accessed Directly from Firewall</entry>
</row>
<row>
<entry>loc2</entry>
<entry>Local2</entry>
<entry>Hosts accessed via internal Router</entry>
</row>
</tbody>
</tgroup>
</table>
<note>
<para>Here it doesn&#39;t matter which zone is defined first.</para>
</note>
<table>
<title>/etc/shorewall/interfaces</title>
<tgroup cols="4">
<thead>
<row>
<entry align="center">ZONE</entry>
<entry align="center">INTERFACE</entry>
<entry align="center">BROADCAST</entry>
<entry align="center">OPTIONS</entry>
</row>
</thead>
<tbody>
<row>
<entry>-</entry>
<entry>eth1</entry>
<entry>192.168.1.255</entry>
<entry>...</entry>
</row>
</tbody>
</tgroup>
</table>
<table>
<title>/etc/shorewall/hosts</title>
<tgroup cols="3">
<thead>
<row>
<entry align="center">ZONE</entry>
<entry align="center">HOSTS</entry>
<entry align="center">OPTIONS</entry>
</row>
</thead>
<tbody>
<row>
<entry>loc1</entry>
<entry>eth1:192.168.1.0/24</entry>
<entry></entry>
</row>
<row>
<entry>loc2</entry>
<entry>eth1:192.168.2.0/24</entry>
<entry></entry>
</row>
</tbody>
</tgroup>
</table>
<para>If you don&#39;t need Shorewall to set up infrastructure to
route traffic between &#39;loc&#39; and &#39;loc1&#39;, add these two
policies:</para>
<table>
<title>/etc/shorewall/policy</title>
<tgroup cols="5">
<thead>
<row>
<entry align="center">SOURCE</entry>
<entry align="center">DEST</entry>
<entry align="center">POLICY</entry>
<entry align="center">LOG LEVEL</entry>
<entry align="center">RATE:BURST</entry>
</row>
</thead>
<tbody>
<row>
<entry>loc</entry>
<entry>loc1</entry>
<entry>NONE</entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry>loc1</entry>
<entry>loc</entry>
<entry>NONE</entry>
<entry></entry>
<entry></entry>
</row>
</tbody>
</tgroup>
</table>
</section>
</section>
</section>
<section>
<title>Some Hosts have Special Firewalling Requirements</title>
<para>There are cases where a subset of the addresses associated with an
interface need special handling. Here&#39;s an example.</para>
<graphic fileref="images/MultiZone2.png" />
<para>In this example, addresses 192.168.1.8 - 192.168.1.15
(192.168.1.8/29) are to be treated as their own zone (loc1).</para>
<table>
<title>/etc/shorewall/zones</title>
<tgroup cols="3">
<thead>
<row>
<entry align="center">ZONE</entry>
<entry align="center">DISPLAY</entry>
<entry align="center">COMMENTS</entry>
</row>
</thead>
<tbody>
<row>
<entry>loc1</entry>
<entry>Local2</entry>
<entry>192.168.1.8 - 192.168.1.15</entry>
</row>
<row>
<entry>loc</entry>
<entry>Local</entry>
<entry>All hosts accessed via eth1</entry>
</row>
</tbody>
</tgroup>
</table>
<note>
<para>the sub-zone (loc1) is defined first!</para>
</note>
<table>
<title>/etc/shorewall/interfaces</title>
<tgroup cols="4">
<thead>
<row>
<entry align="center">ZONE</entry>
<entry align="center">INTERFACE</entry>
<entry align="center">BROADCAST</entry>
<entry align="center">OPTIONS</entry>
</row>
</thead>
<tbody>
<row>
<entry>loc</entry>
<entry>eth1</entry>
<entry>192.168.1.255</entry>
<entry>...</entry>
</row>
</tbody>
</tgroup>
</table>
<table>
<title>/etc/shorewall/hosts</title>
<tgroup cols="3">
<thead>
<row>
<entry align="center">ZONE</entry>
<entry align="center">HOSTS</entry>
<entry align="center">OPTIONS</entry>
</row>
</thead>
<tbody>
<row>
<entry>loc1</entry>
<entry>eth1:192.168.2.0/24</entry>
<entry></entry>
</row>
</tbody>
</tgroup>
</table>
<para>You probably don&#39;t want Shorewall to set up infrastructure to
route traffic between &#39;loc&#39; and &#39;loc1&#39; so you should add
these two policies:</para>
<table>
<title>/etc/shorewall/policy</title>
<tgroup cols="5">
<thead>
<row>
<entry align="center">SOURCE</entry>
<entry align="center">DEST</entry>
<entry align="center">POLICY</entry>
<entry align="center">LOG LEVEL</entry>
<entry align="center">RATE:BURST</entry>
</row>
</thead>
<tbody>
<row>
<entry>loc</entry>
<entry>loc1</entry>
<entry>NONE</entry>
<entry></entry>
<entry></entry>
</row>
<row>
<entry>loc1</entry>
<entry>loc</entry>
<entry>NONE</entry>
<entry></entry>
<entry></entry>
</row>
</tbody>
</tgroup>
</table>
</section>
</article>