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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Standalone Firewall</title><link rel="stylesheet" href="html.css" type="text/css" /><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><div class="article" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title"><a id="standalone"></a>Standalone Firewall</h2></div><div><div class="authorgroup"><div class="author"><h3 class="author"><span class="firstname">Tom</span> <span class="surname">Eastep</span></h3></div></div></div><div><p class="copyright">Copyright © 2002-2007 Thomas M. Eastep</p></div><div><div class="legalnotice"><a id="id289810"></a><p>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
“<span class="quote"><a class="ulink" href="GnuCopyright.htm" target="_self">GNU Free Documentation
License</a></span>”.</p></div></div><div><p class="pubdate">2008/12/15</p></div></div><hr /></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#Introduction">Introduction</a></span></dt><dd><dl><dt><span class="section"><a href="#System">System Requirements</a></span></dt><dt><span class="section"><a href="#Before">Before you start</a></span></dt><dt><span class="section"><a href="#Conventions">Conventions</a></span></dt></dl></dd><dt><span class="section"><a href="#PPTP">PPTP/ADSL</a></span></dt><dt><span class="section"><a href="#Concepts">Shorewall Concepts</a></span></dt><dt><span class="section"><a href="#External">External Interface</a></span></dt><dt><span class="section"><a href="#Addresses">IP Addresses</a></span></dt><dt><span class="section"><a href="#Logging">Logging</a></span></dt><dt><span class="section"><a href="#Open">Enabling other Connections</a></span></dt><dt><span class="section"><a href="#Starting">Starting and Stopping Your Firewall</a></span></dt><dt><span class="section"><a href="#Problems">If it Doesn't Work</a></span></dt><dt><span class="section"><a href="#Other">Additional Recommended Reading</a></span></dt></dl></div><div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Caution</h3><p><span class="bold"><strong>This article applies to Shorewall 4.0 and
later. If you are running a version of Shorewall earlier than Shorewall
4.0.0 then please see the documentation for that
release.</strong></span></p></div><div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Caution</h3><p><span class="bold"><strong>Do not attempt to install Shorewall on a
remote system. You are virtually assured to lock yourself out of that
system.</strong></span></p></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Introduction"></a>Introduction</h2></div></div></div><p>Setting up Shorewall on a standalone Linux system is very easy if
you understand the basics and follow the documentation.</p><p>This guide doesn't attempt to acquaint you with all of the features
of Shorewall. It rather focuses on what is required to configure Shorewall
in one of its most common configurations:</p><div class="itemizedlist"><ul type="disc"><li><p>Linux system</p></li><li><p>Single external <acronym class="acronym">IP</acronym> address</p></li><li><p>Connection through Cable Modem, <acronym class="acronym">DSL</acronym>,
<acronym class="acronym">ISDN</acronym>, Frame Relay, dial-up... or connected to a
<acronym class="acronym">LAN</acronym> and you simply wish to protect your Linux
system from other systems on that <acronym class="acronym">LAN</acronym>.</p></li></ul></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="System"></a>System Requirements</h3></div></div></div><p>Shorewall requires that you have the
<span class="command"><strong>iproute</strong></span>/<span class="command"><strong>iproute2</strong></span> package installed
(on<span class="trademark"> RedHat</span>™, the package is called
<span class="command"><strong>iproute</strong></span>). You can tell if this package is installed
by the presence of an <span class="command"><strong>ip</strong></span> program on your firewall
system. As root, you can use the <span class="command"><strong>which</strong></span> command to
check for this program:</p><pre class="programlisting">[root@gateway root]# <span class="command"><strong>which ip</strong></span>
/sbin/ip
[root@gateway root]#</pre></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="Before"></a>Before you start</h3></div></div></div><p>I recommend that you read through the guide first to familiarize
yourself with what's involved then go back through it again making your
configuration changes.</p><div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Caution</h3><p>If you edit your configuration files on a
<span class="trademark">Windows</span>™ system, you must save them as
<span class="trademark">Unix</span>™ files if your editor supports that option
or you must run them through <span class="command"><strong>dos2unix</strong></span> before trying
to use them. Similarly, if you copy a configuration file from your
<span class="trademark">Windows</span>™ hard drive to a floppy disk, you must
run <span class="command"><strong>dos2unix</strong></span> against the copy before using it with
Shorewall. </p><div class="itemizedlist"><ul type="disc"><li><p><a class="ulink" href="http://www.simtel.net/pub/pd/51438.html" target="_self"><span class="trademark">Windows</span>™
Version of <span class="command"><strong>dos2unix</strong></span></a></p></li><li><p><a class="ulink" href="http://www.megaloman.com/%7Ehany/software/hd2u/" target="_self">Linux
Version of <span class="command"><strong>dos2unix</strong></span></a></p></li></ul></div></div></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="Conventions"></a>Conventions</h3></div></div></div><p>Points at which configuration changes are recommended are flagged
with <img src="images/BD21298_.gif" />.</p></div></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="PPTP"></a>PPTP/ADSL</h2></div></div></div><p><img src="images/BD21298_.gif" /></p><p>If you have an <acronym class="acronym">ADSL</acronym> Modem and you use
<acronym class="acronym">PPTP</acronym> to communicate with a server in that modem, you
must make the changes recommended <a class="ulink" href="PPTP.htm#PPTP_ADSL" target="_self">here</a> in addition to those detailed below.
<acronym class="acronym">ADSL</acronym> with <acronym class="acronym">PPTP</acronym> is most commonly
found in Europe, notably in Austria.</p></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Concepts"></a>Shorewall Concepts</h2></div></div></div><p><img src="images/BD21298_.gif" /></p><p>The configuration files for Shorewall are contained in the directory
<code class="filename">/etc/shorewall</code> -- for simple
setups, you only need to deal with a few of these as described in this
guide. After you have <a class="ulink" href="Install.htm" target="_self">installed
Shorewall</a>, you can find the Samples as follows:</p><div class="orderedlist"><ol type="1"><li><p>If you installed using an <acronym class="acronym">RPM</acronym>, the samples
will be in the <code class="filename">Samples/one-interface</code> subdirectory of the
Shorewall documentation directory. If you don't know where the
Shorewall documentation directory is, you can find the samples using
this command:</p><pre class="programlisting">~# rpm -ql shorewall-common | fgrep one-interface
/usr/share/doc/packages/shorewall/Samples/one-interface
/usr/share/doc/packages/shorewall/Samples/one-interface/interfaces
/usr/share/doc/packages/shorewall/Samples/one-interface/policy
/usr/share/doc/packages/shorewall/Samples/one-interface/rules
/usr/share/doc/packages/shorewall/Samples/one-interface/zones
~#</pre></li><li><p>If you installed using the tarball, the samples are in the
<code class="filename">Samples/one-interface</code> directory
in the tarball.</p></li><li><p>If you installed using a Shorewall 3.x .deb, the samples are in
<code class="filename">/usr/share/doc/shorewall/examples/one-interface</code>.
You must install the shorewall-doc package.</p></li><li><p>If you installed using a Shorewall 4.x .deb, the samples are in
<code class="filename">/usr/share/doc/shorewall-common/examples/one-interface</code>..
You do not need the shorewall-doc package to have access to the
samples.</p></li></ol></div><div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Warning</h3><p><span class="bold"><strong>Note to Debian Users</strong></span></p><p>If you install using the .deb, you will find that your <code class="filename">/etc/shorewall</code> directory is empty. This is
intentional. The released configuration file skeletons may be found on
your system in the directory <code class="filename">/usr/share/doc/shorewall-common/default-config</code>.
Simply copy the files you need from that directory to <code class="filename">/etc/shorewall</code> and modify the
copies.</p></div><p>If you are installing Shorewall version 3.4.0 or later then as each
file is introduced, I suggest that you look at the actual file on your
system and that you look at the <a class="ulink" href="configuration_file_basics.htm#Manpages" target="_self">man page</a> for that
file. For example, to look at the man page for the
<code class="filename">/etc/shorewall/zones</code> file, type <span class="command"><strong>man
shorewall-zones</strong></span> at a shell prompt.</p><p>If you are installing a Shorewall version earlier than 3.4.0, then
as each file is introduced, I suggest that you look through the actual
file on your system -- each file contains detailed configuration
instructions and default entries.</p><p>Shorewall views the network where it is running as being composed of
a set of <span class="emphasis"><em>zones</em></span>. In the one-interface sample
configuration, only two zones are defined:</p><pre class="programlisting">#ZONE TYPE OPTIONS IN OUT
# OPTIONS OPTIONS
fw firewall
net ipv4</pre><p>Shorewall zones are defined in <a class="ulink" href="manpages/shorewall-zones.html" target="_self"><code class="filename">/etc/shorewall/zones</code></a>.</p><p>Note that Shorewall recognizes the firewall system as its own zone.
When the <code class="filename">/etc/shorewall/zones</code> file is processed, the
name of the firewall zone (“<span class="quote">fw</span>” in the above example) is
stored in the shell variable <em class="firstterm">$FW</em> which may be used
to refer to the firewall zone throughout the Shorewall
configuration.</p><p>Rules about what traffic to allow and what traffic to deny are
expressed in terms of zones.</p><div class="itemizedlist"><ul type="disc"><li><p>You express your default policy for connections from one zone to
another zone in the <a class="ulink" href="manpages/shorewall-policy.html" target="_self"><code class="filename">/etc/shorewall/policy</code></a>
file.</p></li><li><p>You define exceptions to those default policies in the <a class="ulink" href="manpages/shorewall-rules.html" target="_self"><code class="filename">/etc/shorewall/rules</code></a>
file.</p></li></ul></div><p>For each connection request entering the firewall, the request is
first checked against the
<code class="filename"><code class="filename">/etc/shorewall/rules</code></code> file. If no
rule in that file matches the connection request then the first policy in
<code class="filename">/etc/shorewall/policy</code> that matches the request is
applied. If there is a <a class="ulink" href="shorewall_extension_scripts.htm" target="_self">common
action</a> defined for the policy in
<code class="filename">/etc/shorewall/actions</code> or
<code class="filename">/usr/share/shorewall/actions.std</code> then that action is
performed before the policy is applied. The purpose of the common action is
two-fold:</p><div class="itemizedlist"><ul type="disc"><li><p>It silently drops or rejects harmless common traffic that would
otherwise clutter up your log — Broadcasts for example.</p></li><li><p>If ensures that traffic critical to correct operation is allowed
through the firewall — ICMP <span class="emphasis"><em>fragmentation-needed</em></span>
for example.</p></li></ul></div><p>The <code class="filename">/etc/shorewall/policy</code> file included with
the one-interface sample has the following policies:</p><pre class="programlisting">#SOURCE ZONE DESTINATION ZONE POLICY LOG LEVEL LIMIT:BURST
$FW net ACCEPT
net all DROP info
all all REJECT info</pre><p>The above policy will:</p><div class="orderedlist"><ol type="1"><li><p>allow all connection requests from the firewall to the
Internet</p></li><li><p>drop (ignore) all connection requests from the Internet to your
firewall</p></li><li><p>reject all other connection requests (Shorewall requires this
catchall policy).</p></li></ol></div><p>The word <em class="firstterm">info</em> in the LOG LEVEL column for the
last two policies indicates that packets dropped or rejected under those
policies should be <a class="ulink" href="shorewall_logging.html" target="_self">logged at that
level</a>.</p><p>At this point, edit your <code class="filename">/etc/shorewall/policy</code>
and make any changes that you wish.</p></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="External"></a>External Interface</h2></div></div></div><p>The firewall has a single network interface. Where Internet
connectivity is through a cable or <acronym class="acronym">DSL</acronym>
“<span class="quote">Modem</span>”, the <span class="emphasis"><em>External Interface</em></span> will be
the Ethernet adapter (<code class="filename">eth0</code>) that
is connected to that “<span class="quote">Modem</span>” <span class="underline">unless</span> you connect via
<span class="emphasis"><em>Point-to-Point Protocol over Ethernet</em></span>
(<acronym class="acronym">PPPoE</acronym>) or <span class="emphasis"><em>Point-to-Point Tunneling
Protocol</em></span> (<acronym class="acronym">PPTP</acronym>) in which case the External
Interface will be a <acronym class="acronym">PPP</acronym> interface (e.g., <code class="filename">ppp0</code>). If you connect via a regular modem,
your External Interface will also be <code class="filename">ppp0</code>. If you connect using
<acronym class="acronym">ISDN</acronym>, your external interface will be <code class="filename">ippp0</code>.</p><div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Caution</h3><p>Be sure you know which interface is your external interface. Many
hours have been spent floundering by users who have configured the wrong
interface. If you are unsure, then as root type <span class="command"><strong>ip route
ls</strong></span> at the command line. The device listed in the last
(default) route should be your external interface.</p><p>Example:</p><pre class="programlisting">root@lists:~# ip route ls
192.168.2.2 dev tun0 proto kernel scope link src 192.168.2.1
10.13.10.0/24 dev tun1 scope link
192.168.2.0/24 via 192.168.2.2 dev tun0
206.124.146.0/24 dev eth0 proto kernel scope link src 206.124.146.176
10.10.10.0/24 dev tun1 scope link
default via 206.124.146.254 dev <span class="bold"><strong>eth0</strong></span>
root@lists:~# </pre><p>In that example, <code class="filename">eth0</code> is
the external interface.</p></div><p><img src="images/BD21298_.gif" /></p><p>The Shorewall one-interface sample configuration assumes that the
external interface is <code class="filename">eth0</code>. If
your configuration is different, you will have to modify the sample
<code class="filename">/etc/shorewall/interfaces</code> file accordingly. While you
are there, you may wish to review the list of options that are specified
for the interface. Some hints:</p><div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Tip</h3><p>If your external interface is <code class="filename">ppp0</code> or <code class="filename">ippp0</code>, you can replace the
“<span class="quote">detect</span>” in the second column with “<span class="quote">-</span>” (minus
the quotes).</p></div><div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Tip</h3><p>If your external interface is <code class="filename">ppp0</code> or <code class="filename">ippp0</code> or if you have a static IP address,
you can remove “<span class="quote">dhcp</span>” from the option list.</p></div></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Addresses"></a>IP Addresses</h2></div></div></div><p>Before going further, we should say a few words about
<span class="emphasis"><em>Internet Protocol</em></span> (<acronym class="acronym">IP</acronym>) addresses.
Normally, your <span class="emphasis"><em>Internet Service Provider</em></span>
(<acronym class="acronym">ISP</acronym>) will assign you a single <acronym class="acronym">IP</acronym>
address. That address can be assigned statically, by the <span class="emphasis"><em>Dynamic
Host Configuration Protocol</em></span> (<acronym class="acronym">DHCP</acronym>), through
the establishment of your dial-up connection, or during establishment of
your other type of <acronym class="acronym">PPP</acronym> (<acronym class="acronym">PPPoA</acronym>,
<acronym class="acronym">PPPoE</acronym>, etc.) connection.</p><p><span class="bold"><strong>RFC-1918</strong></span> reserves several
<span class="emphasis"><em>Private</em></span> <acronym class="acronym">IP</acronym> address ranges for use
in private networks:</p><pre class="programlisting">10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255</pre><p>These addresses are sometimes referred to as
<span class="emphasis"><em>non-routable</em></span> because the Internet backbone routers
will not forward a packet whose destination address is reserved by
<span class="bold"><strong>RFC-1918</strong></span>. In some cases though,
<acronym class="acronym">ISP</acronym>s are assigning these addresses then using
<span class="emphasis"><em>Network Address Translation</em></span> <span class="emphasis"><em>-
</em></span><acronym class="acronym">NAT</acronym>) to rewrite packet headers when
forwarding to/from the Internet.</p><p><img src="images/BD21298_.gif" /></p><p>Before starting Shorewall, <span class="bold"><strong>you should look at
the IP address of your external interface and if it is in one of the above
ranges, you should remove the “<span class="quote">norfc1918</span>” option from the
entry in <code class="filename">/etc/shorewall/interfaces</code>.</strong></span></p><div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Tip</h3><p>To determine the IP address of your external interface, as root
type <span class="command"><strong>ip addr ls dev <interface></strong></span> at the
command line where <<span class="emphasis"><em>interface</em></span>> is your
external interface. The line beginning with <span class="emphasis"><em>inet</em></span>
identifies your IP address.</p><p>Example:</p><pre class="programlisting">root@lists:~# ip addr ls dev eth0
2: eth0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc htb qlen 1000
link/ether 00:02:e3:08:48:4c brd ff:ff:ff:ff:ff:ff
inet <span class="bold"><strong>206.124.146.176</strong></span>/24 brd 206.124.146.255 scope global eth0
inet6 fe80::202:e3ff:fe08:484c/64 scope link
valid_lft forever preferred_lft forever
root@lists:~# </pre><p>In this example, the IP address of the external interface is
206.124.146.176</p></div></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Logging"></a>Logging</h2></div></div></div><p>Shorewall does not maintain a log itself but rather relies on your
<a class="ulink" href="shorewall_logging.html" target="_self">system's logging
configuration</a>. The following <a class="ulink" href="manpages/shorewall.html" target="_self">commands</a> rely on knowing where
Netfilter messages are logged:</p><div class="itemizedlist"><ul type="disc"><li><p><span class="command"><strong>shorewall show log</strong></span> (Displays the last 20
Netfilter log messages)</p></li><li><p><span class="command"><strong>shorewall logwatch</strong></span> (Polls the log at a
settable interval</p></li><li><p><span class="command"><strong>shorewall dump</strong></span> (Produces an extensive report
for inclusion in Shorewall problem reports)</p></li></ul></div><p>It is important that these commands work properly because when you
encounter connection problems when Shorewall is running, the first thing
that you should do is to look at the Netfilter log; with the help of
<a class="ulink" href="FAQ.htm#faq17" target="_self">Shorewall FAQ 17</a>, you can usually
resolve the problem quickly.</p><p>Most commonly, Netfilter messages are logged to
<code class="filename">/var/log/messages</code>. Recent
<span class="trademark">SuSE/OpenSuSE</span>™ releases come preconfigured with
syslog-ng and log Netfilter messages to
<code class="filename">/var/log/firewall</code>.</p><p><img src="images/BD21298_.gif" /></p><p>If you are running a distribution that logs Netfilter messages to a
log other than <code class="filename">/var/log/messages</code>, then modify the
LOGFILE setting in <code class="filename">/etc/shorewall/shorewall.conf</code> to
specify the name of your log.</p><div class="important" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Important</h3><p>The LOGFILE setting does not control where the Netfilter log is
maintained -- it simply tells the /sbin/<code class="filename">shorewall</code>
utility where to find the log.</p></div></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Open"></a>Enabling other Connections</h2></div></div></div><p>Shorewall includes a collection of macros that can be used to
quickly allow or deny services. You can find a list of the macros included
in your version of Shorewall using the command <span class="command"><strong>ls
<code class="filename">/usr/share/shorewall/macro.*</code></strong></span>.</p><p>If you wish to enable connections from the Internet to your firewall
and you find an appropriate macro in
<code class="filename">/etc/shorewall/macro.*</code>, the general format of a rule
in <code class="filename">/etc/shorewall/rules</code> is:</p><pre class="programlisting">#ACTION SOURCE DESTINATION PROTO DEST PORT(S)
<<span class="emphasis"><em>macro</em></span>>/ACCEPT net $FW</pre><div class="important" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Important</h3><p>Be sure to add your rules after the line that reads <span class="bold"><strong>SECTION NEW.</strong></span></p></div><div class="example"><a id="Example1"></a><p class="title"><b>Example 1. You want to run a Web Server and a IMAP Server on your firewall
system:</b></p><div class="example-contents"><pre class="programlisting">#ACTION SOURCE DESTINATION PROTO DEST PORT(S)
Web/ACCEPT net $FW
IMAP/ACCEPT net $FW</pre></div></div><br class="example-break" /><p>You may also choose to code your rules directly without using the
pre-defined macros. This will be necessary in the event that there is not
a pre-defined macro that meets your requirements. In that case the general
format of a rule in <code class="filename">/etc/shorewall/rules</code> is:</p><pre class="programlisting">#ACTION SOURCE DESTINATION PROTO DEST PORT(S)
ACCEPT net $FW <span class="emphasis"><em><protocol></em></span> <span class="emphasis"><em><port></em></span></pre><div class="example"><a id="Example2"></a><p class="title"><b>Example 2. You want to run a Web Server and a IMAP Server on your firewall
system:</b></p><div class="example-contents"><pre class="programlisting">#ACTION SOURCE DESTINATION PROTO DEST PORT(S)
ACCEPT net $FW tcp 80
ACCEPT net $FW tcp 143</pre></div></div><br class="example-break" /><p>If you don't know what port and protocol a particular application
uses, see <a class="ulink" href="ports.htm" target="_self">here</a>.</p><div class="important" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Important</h3><p>I don't recommend enabling telnet to/from the Internet because it
uses clear text (even for login!). If you want shell access to your
firewall from the Internet, use <acronym class="acronym">SSH</acronym>:</p><pre class="programlisting">#ACTION SOURCE DESTINATION PROTO DEST PORT(S)
SSH/ACCEPT net $FW </pre></div><p><img src="images/BD21298_.gif" /></p><p>At this point, edit <code class="filename">/etc/shorewall/rules</code> to add
other connections as desired.</p></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Starting"></a>Starting and Stopping Your Firewall</h2></div></div></div><p><img src="images/BD21298_.gif" /></p><p>The <a class="ulink" href="Install.htm" target="_self">installation procedure</a>
configures your system to start Shorewall at system boot but startup is
disabled so that your system won't try to start Shorewall before
configuration is complete. Once you have completed configuration of your
firewall, you must edit /etc/shorewall/shorewall.conf and set
STARTUP_ENABLED=Yes.</p><div class="important" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Important</h3><p>Users of the .deb package must edit
<code class="filename">/etc/default/shorewall</code> and set
<code class="varname">STARTUP=1.</code></p></div><div class="important" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Important</h3><p>You must enable startup by editing
<code class="filename">/etc/shorewall/shorewall.conf</code> and setting
<code class="varname">STARTUP_ENABLED=Yes.</code></p></div><p>The firewall is started using the “<span class="quote"><span class="command"><strong>shorewall
start</strong></span></span>” command and stopped using
“<span class="quote"><span class="command"><strong>shorewall stop</strong></span></span>”. When the firewall is
stopped, routing is enabled on those hosts that have an entry in
<code class="filename"><a class="ulink" href="manpages/shorewall-routestopped.html" target="_self">/etc/shorewall/routestopped</a></code>.
A running firewall may be restarted using the “<span class="quote"><span class="command"><strong>shorewall
restart</strong></span></span>” command. If you want to totally remove any trace
of Shorewall from your Netfilter configuration, use
“<span class="quote"><span class="command"><strong>shorewall clear</strong></span></span>”.</p><div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Warning</h3><p>If you are connected to your firewall from the Internet, do not
issue a “<span class="quote"><span class="command"><strong>shorewall stop</strong></span></span>” command unless
you have added an entry for the IP address that you are connected from
to <a class="ulink" href="manpages/shorewall-routestopped.html" target="_self"><code class="filename">/etc/shorewall/routestopped</code></a>.
Also, I don't recommend using “<span class="quote"><span class="command"><strong>shorewall
restart</strong></span></span>”; it is better to create an <span class="emphasis"><em><a class="ulink" href="configuration_file_basics.htm#Configs" target="_self">alternate
configuration</a></em></span> and test it using the <a class="ulink" href="starting_and_stopping_shorewall.htm" target="_self">“<span class="quote"><span class="command"><strong>shorewall
try</strong></span></span>”</a> command.</p></div></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Problems"></a>If it Doesn't Work</h2></div></div></div><div class="itemizedlist"><ul type="disc"><li><p>Re-check each of the items flagged with a red arrow
above.</p></li><li><p>Check your <a class="ulink" href="shorewall_logging.html" target="_self">log</a>.</p></li><li><p>Check the <a class="ulink" href="troubleshoot.htm" target="_self">Troubleshooting
Guide</a>.</p></li><li><p>Check the <a class="ulink" href="FAQ.htm" target="_self">FAQ</a>.</p></li></ul></div></div><div class="section" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Other"></a>Additional Recommended Reading</h2></div></div></div><p>I highly recommend that you review the <a class="ulink" href="configuration_file_basics.htm" target="_self">Common Configuration File Features
page</a> -- it contains helpful tips about Shorewall features than
make administering your firewall easier.</p></div></div></body></html>
