forked from extern/shorewall_code
c2ccd7fd3d
git-svn-id: https://shorewall.svn.sourceforge.net/svnroot/shorewall/trunk@800 fbd18981-670d-0410-9b5c-8dc0c1a9a2bb
337 lines
14 KiB
HTML
337 lines
14 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<meta http-equiv="Content-Language" content="en-us">
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<meta name="GENERATOR" content="Microsoft FrontPage 5.0">
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<meta name="ProgId" content="FrontPage.Editor.Document">
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<meta http-equiv="Content-Type"
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content="text/html; charset=windows-1252">
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<title>Configuration File Basics</title>
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</head>
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<body>
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<h1 style="text-align: center;">Configuration Files<br>
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</h1>
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<p><b><font color="#ff0000">Warning: </font>If you copy or edit your
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configuration files on a system running Microsoft Windows, you <u>must</u>
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run them through <a
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href="http://www.megaloman.com/%7Ehany/software/hd2u/"> dos2unix</a>
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before you use them with Shorewall.</b></p>
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<h2><a name="Files"></a>Files</h2>
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<p>Shorewall's configuration files are in the directory /etc/shorewall.</p>
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<ul>
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<li>/etc/shorewall/shorewall.conf - used to
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set several firewall parameters.</li>
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<li>/etc/shorewall/params - use this file to set shell variables that
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you will expand in other files.</li>
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<li>/etc/shorewall/zones - partition the firewall's view of the world
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into <i>zones.</i></li>
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<li>/etc/shorewall/policy - establishes firewall high-level policy.</li>
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<li>/etc/shorewall/interfaces - describes the interfaces on the
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firewall system.</li>
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<li>/etc/shorewall/hosts - allows defining zones in terms of
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individual hosts and subnetworks.</li>
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<li>/etc/shorewall/masq - directs the firewall where to use
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many-to-one (dynamic) Network Address Translation (a.k.a. Masquerading)
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and Source Network Address Translation (SNAT).</li>
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<li>/etc/shorewall/modules - directs the firewall to load kernel
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modules.</li>
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<li>/etc/shorewall/rules - defines rules that are exceptions to the
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overall policies established in /etc/shorewall/policy.</li>
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<li>/etc/shorewall/nat - defines one-to-one NAT
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rules.</li>
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<li>/etc/shorewall/proxyarp - defines use of Proxy ARP.</li>
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<li>/etc/shorewall/routestopped (Shorewall 1.3.4 and later) - defines
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hosts accessible when Shorewall is stopped.</li>
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<li>/etc/shorewall/tcrules - defines marking of packets for later use
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by traffic control/shaping or policy routing.</li>
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<li>/etc/shorewall/tos - defines rules for setting the TOS field in
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packet headers.</li>
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<li>/etc/shorewall/tunnels - defines IPSEC,
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GRE and IPIP tunnels with end-points on the firewall system.</li>
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<li>/etc/shorewall/blacklist - lists blacklisted IP/subnet/MAC
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addresses.</li>
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<li>/etc/shorewall/init - commands that you wish to execute at
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the beginning of a "shorewall start" or "shorewall restart".</li>
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<li>/etc/shorewall/start - commands that you wish to execute at the
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completion of a "shorewall start" or "shorewall restart"</li>
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<li>/etc/shorewall/stop - commands that you wish to execute at
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the beginning of a "shorewall stop".</li>
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<li>/etc/shorewall/stopped - commands that you wish to execute
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at the completion of a "shorewall stop".</li>
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<li>/etc/shorewall/ecn - disable Explicit Congestion Notification
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(ECN - RFC 3168) to remote hosts or networks.</li>
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<li>/etc/shorewall/accounting - define IP traffic accounting rules</li>
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<li>/etc/shorewall/usersets and /etc/shorewall/users - define sets of
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users/groups with
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similar access rights<br>
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</li>
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</ul>
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<h2>Comments</h2>
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<p>You may place comments in configuration files by making the first
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non-whitespace character a pound sign ("#"). You may also place
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comments at the end of any line, again by delimiting the comment from
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the
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rest of the line with a pound sign.</p>
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<p>Examples:</p>
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<pre># This is a comment</pre>
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<pre>ACCEPT net fw tcp www #This is an end-of-line comment</pre>
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<h2><a name="Continuation"></a>Line Continuation</h2>
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<p>You may continue lines in the configuration files using the usual
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backslash ("\") followed immediately by a new line character.</p>
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<p>Example:</p>
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<pre>ACCEPT net fw tcp \<br>smtp,www,pop3,imap #Services running on the firewall</pre>
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<h2><a name="INCLUDE"></a>IN<small><small></small></small>CLUDE
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Directive</h2>
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Beginning with Shorewall version 1.4.2, any file may contain INCLUDE
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directives. An INCLUDE directive consists of the word INCLUDE followed
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by a file name and causes the contents of the named file to be
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logically included into the file containing the INCLUDE. File names
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given in an INCLUDE directive are assumed to reside in /etc/shorewall
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or in an alternate configuration directory if one has been specified
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for the command.<br>
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<br>
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INCLUDE's may be nested to a level of 3 -- further nested INCLUDE
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directives are ignored with a warning message.<big><big><br>
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<br>
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</big></big> Examples:<big> </big> <br>
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<blockquote> shorewall/params.mgmt:<br>
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<blockquote> MGMT_SERVERS=1.1.1.1,2.2.2.2,3.3.3.3<br>
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TIME_SERVERS=4.4.4.4<br>
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BACKUP_SERVERS=5.5.5.5<br>
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</blockquote>
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----- end params.mgmt -----<br>
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</blockquote>
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<blockquote> shorewall/params:<br>
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</blockquote>
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<blockquote>
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<blockquote> # Shorewall 1.3 /etc/shorewall/params<br>
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[..]<br>
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#######################################<br>
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<br>
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INCLUDE params.mgmt <br>
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<br>
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# params unique to this host here<br>
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#LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT
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REMOVE<br>
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</blockquote>
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</blockquote>
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<blockquote> ----- end params -----<br>
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</blockquote>
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<blockquote> shorewall/rules.mgmt:<br>
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</blockquote>
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<blockquote>
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<blockquote> ACCEPT
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net:$MGMT_SERVERS
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$FW tcp 22<br>
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ACCEPT
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$FW
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net:$TIME_SERVERS udp 123<br>
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ACCEPT
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$FW
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net:$BACKUP_SERVERS tcp 22<br>
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</blockquote>
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</blockquote>
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<blockquote> ----- end rules.mgmt -----<br>
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</blockquote>
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<blockquote> shorewall/rules:<br>
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</blockquote>
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<blockquote>
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<blockquote> # Shorewall version 1.3 - Rules File<br>
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[..]<br>
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#######################################<br>
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<br>
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INCLUDE rules.mgmt <br>
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<br>
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# rules unique to this host here<br>
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#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT
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REMOVE<br>
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</blockquote>
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</blockquote>
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<blockquote> ----- end rules -----<br>
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</blockquote>
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<h2><a name="dnsnames"></a>Using DNS Names</h2>
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<p align="left"> </p>
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<p align="left"><b>WARNING: I personally recommend strongly <u>against</u>
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using DNS names in Shorewall configuration files. If you use DNS names
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and you are called out of bed at 2:00AM because Shorewall won't start
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as a result of DNS problems then don't say that you were not
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forewarned. <br>
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</b></p>
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<p align="left"><b> -Tom<br>
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</b></p>
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<p align="left">Beginning with Shorewall 1.3.9, Host addresses in
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Shorewall configuration files may be specified as either IP addresses
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or DNS Names.<br>
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<br>
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DNS names in iptables rules aren't nearly as useful
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as they first appear. When a DNS name appears in a rule, the iptables
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utility resolves the name to one or more IP addresses and inserts those
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addresses into the rule. So changes in the DNS->IP address
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relationship that occur after the firewall has started have absolutely
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no effect on the firewall's ruleset. </p>
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<p align="left"> If your firewall rules include DNS names then:</p>
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<ul>
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<li>If your /etc/resolv.conf is wrong then your firewall won't start.</li>
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<li>If your /etc/nsswitch.conf is wrong then your firewall won't
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start.</li>
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<li>If your Name Server(s) is(are) down then your firewall won't
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start.</li>
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<li>If your startup scripts try to start your firewall before
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starting your DNS server then your firewall won't start.<br>
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</li>
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<li>Factors totally outside your control (your ISP's router is down
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for example), can prevent your firewall from starting.</li>
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<li>You must bring up your network interfaces prior
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to starting your firewall.<br>
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</li>
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</ul>
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<p align="left"> Each DNS name much be fully qualified and include a
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minumum of two periods (although one may be trailing). This restriction
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is imposed by Shorewall to insure backward compatibility with existing
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configuration files.<br>
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<br>
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Examples of valid DNS names:<br>
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</p>
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<ul>
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<li>mail.shorewall.net</li>
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<li>shorewall.net. (note the trailing period).</li>
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</ul>
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Examples of invalid DNS names:<br>
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<ul>
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<li>mail (not fully qualified)</li>
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<li>shorewall.net (only one period)</li>
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</ul>
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DNS names may not be used as:<br>
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<ul>
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<li>The server address in a DNAT rule (/etc/shorewall/rules file)</li>
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<li>In the ADDRESS column of an entry in /etc/shorewall/masq.</li>
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<li>In the /etc/shorewall/nat file.</li>
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</ul>
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These restrictions are not imposed by Shorewall simply for your
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inconvenience but are rather limitations of iptables.<br>
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<h2><a name="Compliment"></a>Complementing an Address or Subnet</h2>
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<p>Where specifying an IP address, a subnet or an interface, you can
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precede the item with "!" to specify the complement of the item. For
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example, !192.168.1.4 means "any host but 192.168.1.4". There must be
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no white space following the "!".</p>
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<h2><a name="Lists"></a>Comma-separated Lists</h2>
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<p>Comma-separated lists are allowed in a number of contexts within the
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configuration files. A comma separated list:</p>
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<ul>
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<li>Must not have any embedded white space.<br>
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Valid: routefilter,dhcp,norfc1918<br>
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Invalid: routefilter,
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dhcp, norfc1818</li>
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<li>If you use line continuation to break a
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comma-separated list, the continuation line(s) must begin
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in column 1 (or there would be embedded white space)</li>
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<li>Entries in a comma-separated list may appear in any order.</li>
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</ul>
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<h2><a name="Ports"></a>Port Numbers/Service Names</h2>
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<p>Unless otherwise specified, when giving a port number you can use
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either an integer or a service name from /etc/services. </p>
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<h2><a name="Ranges"></a>Port Ranges</h2>
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<p>If you need to specify a range of ports, the proper syntax is <<i>low
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port number</i>>:<<i>high port number</i>>. For example, if
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you want to forward the range of tcp ports 4000 through 4100 to local
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host 192.168.1.3, the entry in /etc/shorewall/rules is:<br>
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</p>
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<pre> DNAT net loc:192.168.1.3 tcp 4000:4100<br></pre>
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If you omit the low port number, a value of zero is assumed; if you
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omit the high port number, a value of 65535 is assumed.<br>
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<h2><a name="Variables"></a>Using Shell Variables</h2>
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<p>You may use the /etc/shorewall/params file to set shell variables
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that you can then use in some of the other configuration files.</p>
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<p>It is suggested that variable names begin with an upper case letter<font
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size="1"> </font>to distinguish them from variables used internally
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within the Shorewall programs</p>
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<p>Example:<br>
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</p>
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<p> /etc/shorewall/params<br>
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</p>
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<blockquote>
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<pre>NET_IF=eth0<br>NET_BCAST=130.252.100.255<br>NET_OPTIONS=routefilter,norfc1918<br></pre>
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</blockquote>
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<p> /etc/shorewall/interfaces record:</p>
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<font face="Century Gothic, Arial, Helvetica">
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<blockquote>
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<pre><font face="Courier">net $NET_IF $NET_BCAST $NET_OPTIONS</font></pre>
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</blockquote>
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</font>
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<p> The result will be the same as if the record had
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been written</p>
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<font face="Century Gothic, Arial, Helvetica">
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<blockquote>
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<pre>net eth0 130.252.100.255 routefilter,norfc1918</pre>
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</blockquote>
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</font>
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<p>Variables may be used anywhere in the other configuration files.</p>
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<h2><a name="MAC"></a>Using MAC Addresses</h2>
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<p>Media Access Control (MAC) addresses can be used to specify packet
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source in several of the configuration files. To use this feature, your
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kernel must have MAC Address Match support
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(CONFIG_IP_NF_MATCH_MAC) included.</p>
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<p>MAC addresses are 48 bits wide and each Ethernet Controller has a
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unique MAC address.<br>
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<br>
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In GNU/Linux, MAC addresses are usually written as a series of 6 hex
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numbers separated by colons. Example:<br>
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<br>
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[root@gateway root]# ifconfig eth0<br>
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eth0 Link encap:Ethernet HWaddr <b><u>02:00:08:E3:FA:55</u></b><br>
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inet addr:206.124.146.176
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Bcast:206.124.146.255 Mask:255.255.255.0<br>
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UP BROADCAST RUNNING MULTICAST MTU:1500
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Metric:1<br>
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RX packets:2398102 errors:0 dropped:0
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overruns:0 frame:0<br>
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TX packets:3044698 errors:0 dropped:0
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overruns:0 carrier:0<br>
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collisions:30394 txqueuelen:100<br>
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RX bytes:419871805 (400.4 Mb) TX
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bytes:1659782221 (1582.8 Mb)<br>
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Interrupt:11 Base address:0x1800<br>
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<br>
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Because Shorewall uses colons as a separator for address fields,
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Shorewall requires MAC addresses to be written in another way. In
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Shorewall, MAC addresses begin with a tilde ("~") and consist of 6 hex
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numbers separated by hyphens. In Shorewall, the MAC address in the
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example above would be written "~02-00-08-E3-FA-55".<br>
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</p>
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<p><b>Note: </b>It is not necessary to use the special Shorewall
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notation in the <a href="MAC_Validation.html">/etc/shorewall/maclist</a>
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file.<br>
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</p>
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<h2><a name="Levels"></a>Shorewall Configurations</h2>
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<p> Shorewall allows you to have configuration directories other than
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/etc/shorewall. The <a href="starting_and_stopping_shorewall.htm">shorewall
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check, start and restart</a> commands allow you to specify an alternate
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configuration directory and Shorewall will use the files in the
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alternate directory rather than the corresponding files in
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/etc/shorewall. The alternate directory need not contain a complete
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configuration; those files not in the alternate directory will be read
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from /etc/shorewall.</p>
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<p> This facility permits you to easily create a test or temporary
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configuration by:</p>
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<ol>
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<li> copying the files that need modification from /etc/shorewall to
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a separate directory;</li>
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<li> modify those files in the separate directory; and</li>
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<li> specifying the separate directory in a shorewall start or
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shorewall restart command (e.g., <i><b>shorewall -c /etc/testconfig
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restart</b></i> )</li>
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</ol>
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The <a href="starting_and_stopping_shorewall.htm"><b>try</b> command</a>
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allows you to attempt to restart using an alternate configuration and
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if an
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error occurs to automatically restart the standard configuration.<br>
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<p><font size="2"> Updated 11/20/2003 - <a href="support.htm">Tom
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Eastep</a>
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</font></p>
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<p><font face="Trebuchet MS"><a href="copyright.htm"><font size="2">Copyright</font>
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<EFBFBD> <font size="2">2001, 2002, 2003 Thomas M. Eastep.</font></a></font><br>
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</p>
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<br>
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</body>
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</html>
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