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<title>Multiple Zones per Interface</title>
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<meta name="author" content="Tom Eastep">
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<h2></h2>
<blockquote> </blockquote>
<h1 style="text-align: center;">Multiple Zones per Interface<br>
</h1>
While most configurations can be handled with each of the firewall'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.<br>
<ol>
<li>The interface has multiple addresses on multiple subnetworks.
This case is covered in the <a
href="Shorewall_and_Aliased_Interfaces.html">Aliased Interface
documentation</a>.</li>
<li>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 <a
href="FAQ.htm#faq2">FAQs 2 and 2a</a>.<br>
</li>
<li>There are routers accessible through the interface and you want
to treat the networks accessed through that router as a separate zone.</li>
<li>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.</li>
</ol>
The key points to keep in mind when setting up multiple zones per
interface are:<br>
<ul>
<li>Shorewall generates rules for zones in the order that the zone
declarations appear in /etc/shorewall/zones.</li>
<li>The order of entries in /etc/shorewall/hosts is immaterial as far
as the generated ruleset is concerned.</li>
</ul>
<span style="font-weight: bold;">These examples use the local zone but
the same technique works for any zone. </span>Remember that Shorewall
doesn't have any conceptual knowledge of "Internet", "Local", or "DMZ"
so all zones except the firewall itself ($FW) are the same as far as
Shorewall is concerned.&nbsp; Also, the examples use private (RFC 1918)
addresses but public IP addresses can be used in exactly the same way.<br>
<h2>Router in the Local Zone<br>
</h2>
Here is an example of a router in the local zone.&nbsp; Note that <span
style="font-weight: bold;">the box called "Router" could be a VPN
server</span> or other such device; from the point of view of this
discussion, it makes no difference.<br>
<br>
<div style="text-align: center;"><img src="images/MultiZone1.png"
title="" alt="(Firewall connected to Internal Router)"
style="width: 556px; height: 335px;"><br>
</div>
<blockquote>
<p> </p>
</blockquote>
<blockquote> </blockquote>
<h3>Can You Use the Standard Configuration?<br>
</h3>
In many cases, the <a href="two-interface.htm">standard two-interface
Shorewall setup</a> will work fine in this configuration.&nbsp; It will
work if:<br>
<ul>
<li>The firewall requirements to/from the internet are the same for
192.168.1.0/24 and 192.168.2.0/24.</li>
<li>The hosts in 192.168.1.0/24 know that the route to 192.168.2.0/24
is through the <span style="font-weight: bold;">router.</span></li>
</ul>
All you have to do on the firewall is add a route to 192.168.2.0/24
through the <span style="font-weight: bold;">router</span> and restart
Shorewall.<br>
<h3>Will One Zone be Enough?</h3>
If the firewalling requirements for the two local networks is the same
but the hosts in 192.168.1.0/24 don'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'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:<br>
<ul>
<li>Add a route to 192.168.2.0/24 through the <span
style="font-weight: bold;">Router.</span></li>
<li>Set the 'routeback' and 'newnotsyn' options for eth1 (the local
firewall interface) in /etc/shorewall/interfaces.</li>
<li>Restart Shorewall.<br>
</li>
</ul>
<h3>I Need Separate Zones</h3>
If you need to make 192.168.2.0/24 into it's own zone, you can do it
one of two ways; Nested Zones or Parallel Zones.<br>
<h4>Nested Zones:</h4>
You can define one zone (called it 'loc') as being all hosts connectied
to eth1 and a second zone 'loc1' (192.168.2.0/24) as a sub-zone.<br>
<br>
<div style="text-align: center;"><img src="images/MultiZone1A.png"
title="" alt="" style="width: 607px; height: 415px;"><br>
</div>
<br>
The advantage of this approach is that the zone 'loc1' can use CONTINUE
policies such that if a connection request doesn't match a 'loc1' rule,
it will be matched against the 'loc' rules. For example, if your
loc1-&gt;net policy is CONTINUE then if a connection request from loc1
to the internet doesn't match any rules for loc1-&gt;net then it will
be checked against the loc-&gt;net rules.<br>
<br>
/etc/shorewall/zones:<br>
<br>
<div style="margin-left: 40px;">
<table cellpadding="2" border="1" style="text-align: left;">
<tbody>
<tr>
<td style="vertical-align: top; font-weight: bold;">ZONE<br>
</td>
<td style="vertical-align: top; font-weight: bold;">DISPLAY<br>
</td>
<td style="vertical-align: top; font-weight: bold;">COMMENTS<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">loc1<br>
</td>
<td style="vertical-align: top;">Local2<br>
</td>
<td style="vertical-align: top;">Hosts access through internal
router<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">loc<br>
</td>
<td style="vertical-align: top;">Local<br>
</td>
<td style="vertical-align: top;">All hosts accessed via eth1<br>
</td>
</tr>
</tbody>
</table>
<br>
Note that the sub-zone (loc1) is defined first!<br>
<br>
</div>
/etc/shorewall/interfaces<br>
<br>
<div style="margin-left: 40px;">
<table cellspacing="2" border="1" style="text-align: left;">
<tbody>
<tr>
<td style="vertical-align: top; font-weight: bold;">ZONE<br>
</td>
<td style="vertical-align: top; font-weight: bold;">INTERFACE<br>
</td>
<td style="vertical-align: top; font-weight: bold;">BROADCAST<br>
</td>
<td style="vertical-align: top; font-weight: bold;">OPTIONS<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">loc<br>
</td>
<td style="vertical-align: top;">eth1<br>
</td>
<td style="vertical-align: top;">192.168.1.255<br>
</td>
<td style="vertical-align: top;">...<br>
</td>
</tr>
</tbody>
</table>
<br>
</div>
/etc/shorewall/hosts<br>
<br>
<div style="margin-left: 40px;">
<table cellpadding="2" border="1" style="text-align: left;">
<tbody>
<tr>
<td style="vertical-align: top; font-weight: bold;">ZONE<br>
</td>
<td style="vertical-align: top; font-weight: bold;">HOSTS<br>
</td>
<td style="vertical-align: top; font-weight: bold;">OPTIONS<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">loc1<br>
</td>
<td style="vertical-align: top;">eth1:192.168.2.0/24<br>
</td>
<td style="vertical-align: top;"><br>
</td>
</tr>
</tbody>
</table>
</div>
<br>
If you don't need Shorewall to set up infrastructure to route traffic
between 'loc' and 'loc1', add these two policies:<br>
<br>
<div style="margin-left: 40px;">
<table cellpadding="2" border="1" style="text-align: left;">
<tbody>
<tr>
<td style="vertical-align: top; font-weight: bold;">SOURCE<br>
</td>
<td style="vertical-align: top; font-weight: bold;">DEST<br>
</td>
<td style="vertical-align: top; font-weight: bold;">POLICY<br>
</td>
<td style="vertical-align: top; font-weight: bold;">LOG<br>
LEVEL<br>
</td>
<td style="vertical-align: top; font-weight: bold;">RATE:BURST<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">loc<br>
</td>
<td style="vertical-align: top;">loc1</td>
<td style="vertical-align: top;">NONE<br>
</td>
<td style="vertical-align: top;"><br>
</td>
<td style="vertical-align: top;"><br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">loc1<br>
</td>
<td style="vertical-align: top;">loc<br>
</td>
<td style="vertical-align: top;">NONE<br>
</td>
<td style="vertical-align: top;"><br>
</td>
<td style="vertical-align: top;"> <br>
</td>
</tr>
</tbody>
</table>
</div>
<h4>Parallel Zones:</h4>
You define both zones in the /etc/shorewall/hosts file to create two
disjoint zones.<br>
<br>
<div style="text-align: center;"><img src="images/MultiZone1B.png"
title="" alt="" style="width: 588px; height: 415px;"><br>
</div>
<br>
/etc/shorewall/zones:<br>
<br>
<div style="margin-left: 40px;">
<table cellpadding="2" border="1" style="text-align: left;">
<tbody>
<tr>
<td style="vertical-align: top; font-weight: bold;">ZONE<br>
</td>
<td style="vertical-align: top; font-weight: bold;">DISPLAY<br>
</td>
<td style="vertical-align: top; font-weight: bold;">COMMENTS<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">loc1<br>
</td>
<td style="vertical-align: top;">Local1<br>
</td>
<td style="vertical-align: top;">Hosts accessed Directly from
Firewall<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">loc2<br>
</td>
<td style="vertical-align: top;">Local2<br>
</td>
<td style="vertical-align: top;">Hosts accessed via internal
Router<br>
</td>
</tr>
</tbody>
</table>
<br>
Here it doesn't matter which zone is defined first.<br>
<br>
</div>
/etc/shorewall/interfaces<br>
<br>
<div style="margin-left: 40px;">
<table cellspacing="2" border="1" style="text-align: left;">
<tbody>
<tr>
<td style="vertical-align: top; font-weight: bold;">ZONE<br>
</td>
<td style="vertical-align: top; font-weight: bold;">INTERFACE<br>
</td>
<td style="vertical-align: top; font-weight: bold;">BROADCAST<br>
</td>
<td style="vertical-align: top; font-weight: bold;">OPTIONS<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">-<br>
</td>
<td style="vertical-align: top;">eth1<br>
</td>
<td style="vertical-align: top;">192.168.1.255<br>
</td>
<td style="vertical-align: top;">...<br>
</td>
</tr>
</tbody>
</table>
<br>
</div>
/etc/shorewall/hosts<br>
<br>
<div style="margin-left: 40px;">
<table cellpadding="2" border="1" style="text-align: left;">
<tbody>
<tr>
<td style="vertical-align: top; font-weight: bold;">ZONE<br>
</td>
<td style="vertical-align: top; font-weight: bold;">HOSTS<br>
</td>
<td style="vertical-align: top; font-weight: bold;">OPTIONS<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">loc1<br>
</td>
<td style="vertical-align: top;">eth1:192.168.1.0/24<br>
</td>
<td style="vertical-align: top;"><br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">loc2<br>
</td>
<td style="vertical-align: top;">eth1:192.168.2.0/24<br>
</td>
<td style="vertical-align: top;"><br>
</td>
</tr>
</tbody>
</table>
</div>
<br>
If you don't need Shorewall to set up infrastructure to route traffic
between 'loc' and 'loc1', add these two policies:<br>
<br>
<div style="margin-left: 40px;">
<table cellpadding="2" border="1" style="text-align: left;">
<tbody>
<tr>
<td style="vertical-align: top; font-weight: bold;">SOURCE<br>
</td>
<td style="vertical-align: top; font-weight: bold;">DEST<br>
</td>
<td style="vertical-align: top; font-weight: bold;">POLICY<br>
</td>
<td style="vertical-align: top; font-weight: bold;">LOG<br>
LEVEL<br>
</td>
<td style="vertical-align: top; font-weight: bold;">RATE:BURST<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">loc<br>
</td>
<td style="vertical-align: top;">loc1</td>
<td style="vertical-align: top;">NONE<br>
</td>
<td style="vertical-align: top;"><br>
</td>
<td style="vertical-align: top;"><br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">loc1<br>
</td>
<td style="vertical-align: top;">loc<br>
</td>
<td style="vertical-align: top;">NONE<br>
</td>
<td style="vertical-align: top;"><br>
</td>
<td style="vertical-align: top;"> <br>
</td>
</tr>
</tbody>
</table>
</div>
<h2>Some Hosts have Special Firewalling Requirements</h2>
There are cases where a subset of the addresses associated with an
interface need special handling.&nbsp; Here's an example.<br>
<br>
<div style="text-align: center;"><img src="images/MultiZone2.png"
title="" alt="" style="height: 252px; width: 631px;"><br>
</div>
<br>
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).<br>
<br>
/etc/shorewall/zones:<br>
<br>
<div style="margin-left: 40px;">
<table cellpadding="2" border="1" style="text-align: left;">
<tbody>
<tr>
<td style="vertical-align: top; font-weight: bold;">ZONE<br>
</td>
<td style="vertical-align: top; font-weight: bold;">DISPLAY<br>
</td>
<td style="vertical-align: top; font-weight: bold;">COMMENTS<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">loc1<br>
</td>
<td style="vertical-align: top;">Local2<br>
</td>
<td style="vertical-align: top;">192.168.1.8 - 192.168.1.15<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">loc<br>
</td>
<td style="vertical-align: top;">Local<br>
</td>
<td style="vertical-align: top;">All hosts accessed via eth1<br>
</td>
</tr>
</tbody>
</table>
<br>
Note that the sub-zone (loc1) is defined first!<br>
<br>
</div>
/etc/shorewall/interfaces<br>
<br>
<div style="margin-left: 40px;">
<table cellspacing="2" border="1" style="text-align: left;">
<tbody>
<tr>
<td style="vertical-align: top; font-weight: bold;">ZONE<br>
</td>
<td style="vertical-align: top; font-weight: bold;">INTERFACE<br>
</td>
<td style="vertical-align: top; font-weight: bold;">BROADCAST<br>
</td>
<td style="vertical-align: top; font-weight: bold;">OPTIONS<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">loc<br>
</td>
<td style="vertical-align: top;">eth1<br>
</td>
<td style="vertical-align: top;">192.168.1.255<br>
</td>
<td style="vertical-align: top;">...<br>
</td>
</tr>
</tbody>
</table>
<br>
</div>
/etc/shorewall/hosts<br>
<br>
<div style="margin-left: 40px;">
<table cellpadding="2" border="1" style="text-align: left;">
<tbody>
<tr>
<td style="vertical-align: top; font-weight: bold;">ZONE<br>
</td>
<td style="vertical-align: top; font-weight: bold;">HOSTS<br>
</td>
<td style="vertical-align: top; font-weight: bold;">OPTIONS<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">loc1<br>
</td>
<td style="vertical-align: top;">eth1:192.168.1.8/29<br>
</td>
<td style="vertical-align: top;"><br>
</td>
</tr>
</tbody>
</table>
</div>
<br>
You probably don't want Shorewall to set up infrastructure to route
traffic
between 'loc' and 'loc1' so you should add these two policies:<br>
<div style="margin-left: 40px;"><br>
<table cellpadding="2" border="1" style="text-align: left;">
<tbody>
<tr>
<td style="vertical-align: top; font-weight: bold;">SOURCE<br>
</td>
<td style="vertical-align: top; font-weight: bold;">DEST<br>
</td>
<td style="vertical-align: top; font-weight: bold;">POLICY<br>
</td>
<td style="vertical-align: top; font-weight: bold;">LOG<br>
LEVEL<br>
</td>
<td style="vertical-align: top; font-weight: bold;">RATE:BURST<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">loc<br>
</td>
<td style="vertical-align: top;">loc1</td>
<td style="vertical-align: top;">NONE<br>
</td>
<td style="vertical-align: top;"><br>
</td>
<td style="vertical-align: top;"><br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">loc1<br>
</td>
<td style="vertical-align: top;">loc<br>
</td>
<td style="vertical-align: top;">NONE<br>
</td>
<td style="vertical-align: top;"><br>
</td>
<td style="vertical-align: top;"><br>
</td>
</tr>
</tbody>
</table>
&nbsp;<br>
</div>
<p><font size="2">Last updated 11/21/2003 - </font><font size="2"> <a
href="support.htm">Tom Eastep</a></font> </p>
<a href="copyright.htm"><font size="2">Copyright</font> © <font
size="2">2003 Thomas M. Eastep.</font></a><br>
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