<?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>
<!--$Id$-->
<articleinfo>
<title>Configuration Files</title>
<authorgroup>
<author>
<firstname>Tom</firstname>
<surname>Eastep</surname>
</author>
</authorgroup>
<pubdate><?dbtimestamp format="Y/m/d"?></pubdate>
<copyright>
<year>2001-2007</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
<quote><ulink url="GnuCopyright.htm">GNU Free Documentation
License</ulink></quote>.</para>
</legalnotice>
</articleinfo>
<caution>
<para><emphasis role="bold">This article applies to Shorewall 3.0 and
later. If you are running a version of Shorewall earlier than Shorewall
3.0.0 then please see the documentation for that
release.</emphasis></para>
</caution>
<caution>
<para>If you copy or edit your configuration files on a system running
Microsoft Windows, you must run them through <ulink
url="http://www.megaloman.com/~hany/software/hd2u/">dos2unix</ulink>
before you use them with Shorewall.</para>
</caution>
<section id="Files">
<title>Files</title>
<para><itemizedlist>
<listitem>
<para><filename>/etc/shorewall/shorewall.conf</filename> - used to
set several firewall parameters.</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/params</filename> - use this file to
set shell variables that you will expand in other files.</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/zones</filename> - partition the
firewall's view of the world into zones.</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/policy</filename> - establishes
firewall high-level policy.</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/interfaces</filename> - describes the
interfaces on the firewall system.</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/hosts</filename> - allows defining
zones in terms of individual hosts and subnetworks.</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/masq</filename> - directs the
firewall where to use many-to-one (dynamic) Network Address
Translation (a.k.a. Masquerading) and Source Network Address
Translation (SNAT).</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/modules</filename> - directs the
firewall to load kernel modules.</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/rules</filename> - defines rules that
are exceptions to the overall policies established in
/etc/shorewall/policy.</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/nat</filename> - defines one-to-one
NAT rules.</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/proxyarp</filename> - defines use of
Proxy ARP.</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/routestopped</filename> - defines
hosts accessible when Shorewall is stopped.</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/tcrules </filename>- defines marking
of packets for later use by traffic control/shaping or policy
routing.</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/tos</filename> - defines rules for
setting the TOS field in packet headers.</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/tunnels</filename> - defines tunnels
(VPN) with end-points on the firewall system.</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/blacklist</filename> - lists
blacklisted IP/subnet/MAC addresses.</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/init</filename> - commands that you
wish to execute at the beginning of a <quote>shorewall start</quote>
or <quote>shorewall restart</quote>.</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/start</filename> - commands that you
wish to execute at the completion of a <quote>shorewall
start</quote> or <quote>shorewall restart</quote></para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/stop </filename>- commands that you
wish to execute at the beginning of a <quote>shorewall
stop</quote>.</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/stopped</filename> - commands that
you wish to execute at the completion of a <quote>shorewall
stop</quote>.</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/ecn</filename> - disable Explicit
Congestion Notification (ECN - RFC 3168) to remote hosts or
networks.</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/accounting</filename> - define IP
traffic accounting rules</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/actions</filename> and
<filename>/usr/share/shorewall/action.template</filename> allow
user-defined actions.</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/providers</filename> - defines an
alternate routing table.</para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/route_rules</filename> (Added in
Shorewall 3.2.0) - Defines routing rules to be used in conjunction
with the routing tables devined in
<filename>/etc/shorewall/providers</filename>.</para>
</listitem>
<listitem>
<para><filename>/usr/share/shorewall/actions.std</filename> -
Actions defined by Shorewall.</para>
</listitem>
<listitem>
<para><filename>/usr/share/shorewall/action.*</filename> - Details
of actions defined by Shorewall.</para>
</listitem>
<listitem>
<para><filename>/usr/share/shorewall/macro.*</filename> - Details of
macros defined by Shorewall.</para>
</listitem>
<listitem>
<para><filename>/usr/share/rfc1918</filename> — Defines the behavior
of the 'norfc1918' interface option in
<filename>/etc/shorewall/interfaces</filename>. <emphasis
role="bold">If you need to change this file, copy it to
<filename>/etc/shorewall</filename> and modify the
copy</emphasis>.</para>
</listitem>
</itemizedlist></para>
</section>
<section id="Manpages">
<title>Man Pages</title>
<para>Beginning with Shorewall version 3.4, man pages are provided in
section 5 for each of the Shorewall configuration files. The name of the
page is formed by prefixing the file name with "shorewall-".</para>
<para>Example — To view the manual page for
<filename>/etc/shorewall/interfaces</filename>:</para>
<programlisting>man shorewall-interfaces</programlisting>
<para>The /etc/shorewall/shorewall.conf file is an exception -- the man
page for that file is 'shorewall.conf':</para>
<programlisting>man shorewall.conf</programlisting>
</section>
<section id="Comments">
<title>Comments</title>
<para>You may place comments in configuration files by making the first
non-whitespace character a pound sign (<quote>#</quote>). You may also
place comments at the end of any line, again by delimiting the comment
from the rest of the line with a pound sign.</para>
<example id="comment">
<title>Comments in a Configuration File</title>
<programlisting># This is a comment
ACCEPT net $FW tcp www #This is an end-of-line comment</programlisting>
</example>
</section>
<section id="COMMENT">
<title>Attach Comment to Netfilter Rules</title>
<para>Beginning with Shorewall version 3.3.3, if you kernel and iptables
contain comment match support (see the output of <command>shorewall show
capabilities</command>), then you can attach comments to Netfilter rules.
This feature is available in the following files:</para>
<itemizedlist>
<listitem>
<para><filename>/etc/shorewall/masq</filename></para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/nat</filename></para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/rules</filename></para>
</listitem>
<listitem>
<para><filename>/etc/shorewall/tcrules</filename></para>
</listitem>
<listitem>
<para>Action definition files
(<filename>/etc/shorewall/action.*</filename>)</para>
</listitem>
</itemizedlist>
<para>To attach a comment to one or more rules, insert a record above the
rules that begins with the word COMMENT (must be in all caps). The
remainder of the line is treated as a comment -- that comment will appear
delimited by "/* ... */" in the output of the <command>shorewall[-lite]
show</command> and <command>shorewall[-lite] dump</command> commands. The
comment will be attached to each generated rule until another COMMENT line
appears. To stop attaching comments to rules, simply insert a line that
contains the single word COMMENT.</para>
<para>Example (<filename>/etc/shorewall/rules</filename>):</para>
<programlisting>COMMENT Stop NETBIOS noise
REJECT loc net tcp 137,445
REJECT loc net udp 137:139
COMMENT Stop my idiotic work laptop from sending to the net with an HP source/dest IP address
DROP loc:!192.168.0.0/22 net
COMMENT</programlisting>
<para>Here's the corresponding output from
<filename>/sbin/shorewall-lite</filename>:</para>
<programlisting>gateway:~ # <command>shorewall-lite show loc2net</command>
Shorewall Lite 3.3.3 Chains loc2net at gateway - Mon Oct 16 15:04:52 PDT 2006
Counters reset Mon Oct 16 14:52:17 PDT 2006
Chain loc2net (1 references)
pkts bytes target prot opt in out source destination
0 0 LOG tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:25 LOG flags 0 level 6 prefix `FW:loc2net:REJECT:'
0 0 reject tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:25
0 0 LOG udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpts:1025:1031 LOG flags 0 level 6 prefix `FW:loc2net:REJECT:'
0 0 reject udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpts:1025:1031
0 0 reject tcp -- * * 0.0.0.0/0 0.0.0.0/0 multiport dports 137,445 <emphasis
role="bold">/* Stop NETBIOS noise */</emphasis>
0 0 reject udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpts:137:139 <emphasis
role="bold">/* Stop NETBIOS noise */</emphasis>
0 0 DROP all -- * * !192.168.0.0/22 0.0.0.0/0 <emphasis
role="bold">/* Stop my idiotic work laptop from sending to the net with an HP source/dest IP address */</emphasis>
5 316 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0
gateway:~ #
</programlisting>
</section>
<section id="Continuation">
<title>Line Continuation</title>
<para>You may continue lines in the configuration files using the usual
backslash (<quote>\</quote>) followed immediately by a new line character
(Enter key).</para>
<example id="continuation">
<title>Line Continuation</title>
<programlisting>ACCEPT net $FW tcp \↵
smtp,www,pop3,imap #Services running on the firewall</programlisting>
</example>
</section>
<section id="INCLUDE">
<title>INCLUDE Directive</title>
<para>Any configuration file may contain INCLUDE directives. An INCLUDE
directive consists of the word INCLUDE followed by a path name and causes
the contents of the named file to be logically included into the file
containing the INCLUDE. Relative path names given in an INCLUDE directive
are assumed to reside in /etc/shorewall or in an alternate configuration
directory if one has been specified for the command.</para>
<para>INCLUDE's may be nested to a level of 3 -- further nested INCLUDE
directives are ignored with a warning message.</para>
<caution>
<para>If you are using <ulink
url="CompiledPrograms.html%23Lite">Shorewall Lite</ulink> and are
running a version of Shorewall earlier than 3.2.9, it is not advisable
to use INCLUDE in the <filename>params</filename> file in an export
directory. If you do that, you must ensure that the included file is
also present on the firewall system's <filename
class="directory">/etc/shorewall-lite/</filename> directory.</para>
<para>Beginning with Shorewall version 3.2.9 (3.4.0 RC2), you can set
EXPORTPARAMS=No in <filename>shorewall.conf</filename>. That prevents
the <filename>params</filename> file from being copied into the compiled
script. With EXPORTPARAMS=No, it is perfectly okay to use INCLUDE in the
<filename>params</filename> file.</para>
</caution>
<example id="include">
<title>Use of INCLUDE</title>
<programlisting> shorewall/params.mgmt:
MGMT_SERVERS=1.1.1.1,2.2.2.2,3.3.3.3
TIME_SERVERS=4.4.4.4
BACKUP_SERVERS=5.5.5.5
----- end params.mgmt -----
shorewall/params:
# Shorewall 1.3 /etc/shorewall/params
[..]
#######################################
INCLUDE params.mgmt
# params unique to this host here
#LAST LINE - ADD YOUR ENTRIES ABOVE THIS ONE - DO NOT REMOVE
----- end params -----
shorewall/rules.mgmt:
ACCEPT net:$MGMT_SERVERS $FW tcp 22
ACCEPT $FW net:$TIME_SERVERS udp 123
ACCEPT $FW net:$BACKUP_SERVERS tcp 22
----- end rules.mgmt -----
shorewall/rules:
# Shorewall version 1.3 - Rules File
[..]
#######################################
INCLUDE rules.mgmt
# rules unique to this host here
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
----- end rules -----</programlisting>
</example>
</section>
<section id="dnsnames">
<title>Using DNS Names</title>
<caution>
<para>I personally recommend strongly against using DNS names in
Shorewall configuration files. If you use DNS names and you are called
out of bed at 2:00AM because Shorewall won't start as a result of DNS
problems then don't say that you were not forewarned.</para>
</caution>
<para>Host addresses in Shorewall configuration files may be specified as
either IP addresses or DNS Names.</para>
<para>DNS names in iptables rules aren't nearly as useful as they first
appear. When a DNS name appears in a rule, the iptables utility resolves
the name to one or more IP addresses and inserts those addresses into the
rule. So changes in the DNS->IP address relationship that occur after
the firewall has started have absolutely no effect on the firewall's
ruleset.</para>
<para>If your firewall rules include DNS names then:</para>
<itemizedlist>
<listitem>
<para>If your <filename>/etc/resolv.conf </filename>is wrong then your
firewall won't start.</para>
</listitem>
<listitem>
<para>If your <filename>/etc/nsswitch.conf</filename> is wrong then
your firewall won't start.</para>
</listitem>
<listitem>
<para>If your Name Server(s) is(are) down then your firewall won't
start.</para>
</listitem>
<listitem>
<para>If your startup scripts try to start your firewall before
starting your DNS server then your firewall won't start.</para>
</listitem>
<listitem>
<para>Factors totally outside your control (your ISP's router is down
for example), can prevent your firewall from starting.</para>
</listitem>
<listitem>
<para>You must bring up your network interfaces prior to starting your
firewall.</para>
</listitem>
</itemizedlist>
<para>Each DNS name must be fully qualified and include a minimum of two
periods (although one may be trailing). This restriction is imposed by
Shorewall to insure backward compatibility with existing configuration
files.</para>
<example id="validdns">
<title>Valid DNS Names</title>
<itemizedlist>
<listitem>
<para>mail.shorewall.net</para>
</listitem>
<listitem>
<para>shorewall.net. (note the trailing period).</para>
</listitem>
</itemizedlist>
</example>
<example id="invaliddns">
<title>Invalid DNS Names</title>
<itemizedlist>
<listitem>
<para>mail (not fully qualified)</para>
</listitem>
<listitem>
<para>shorewall.net (only one period)</para>
</listitem>
</itemizedlist>
</example>
<para>DNS names may not be used as:</para>
<itemizedlist>
<listitem>
<para>The server address in a DNAT rule (/etc/shorewall/rules
file)</para>
</listitem>
<listitem>
<para>In the ADDRESS column of an entry in /etc/shorewall/masq.</para>
</listitem>
<listitem>
<para>In the <filename>/etc/shorewall/nat</filename> file.</para>
</listitem>
</itemizedlist>
<para>These restrictions are imposed by Netfilter and not by
Shorewall.</para>
</section>
<section id="Lists">
<title>Comma-separated Lists</title>
<para>Comma-separated lists are allowed in a number of contexts within the
configuration files. A comma separated list:</para>
<itemizedlist>
<listitem>
<para>Must not have any embedded white space.<programlisting> Valid: routefilter,dhcp,norfc1918
Invalid: routefilter, dhcp, norfc1818</programlisting></para>
</listitem>
<listitem>
<para>If you use line continuation to break a comma-separated list,
the continuation line(s) must begin in column 1 (or there would be
embedded white space)</para>
</listitem>
<listitem>
<para>Entries in a comma-separated list may appear in any
order.</para>
</listitem>
</itemizedlist>
</section>
<section id="Compliment">
<title>Complementing an Address or Subnet</title>
<para>Where specifying an IP address, a subnet or an interface, you can
precede the item with <quote>!</quote> to specify the complement of the
item. For example, !192.168.1.4 means <quote>any host but
192.168.1.4</quote>. There must be no white space following the
<quote>!</quote>.</para>
</section>
<section id="Exclusion">
<title>Exclusion Lists</title>
<para>Shorewall 3.0 differs from earlier versions in that in most contexts
where a comma-separated list of addresses is accepted, an
<firstterm>exclusion list</firstterm> may also be included. An exclusion
list is a comma-separated list of addresses that begins with "!".</para>
<para>Example:</para>
<programlisting>!192.168.1.3,192.168.1.12,192.168.1.32/27</programlisting>
<para>The above list refers to "All addresses except 192.168.1.3,
192.168.1.12 and 192.168.1.32-192.168.1.63.</para>
<para>Exclusion lists can also be added after a network address.</para>
<para>Example:</para>
<programlisting>192.168.1.0/24!192.168.1.3,192.168.1.12,192.168.1.32/27</programlisting>
<para>The above list refers to "All addresses in 192.168.1.0-192.168.1.255
except 192.168.1.3, 192.168.1.12 and 192.168.1.32-192.168.1.63.</para>
</section>
<section id="IPRanges">
<title>IP Address Ranges</title>
<para>If you kernel and iptables have iprange match support, you may use
IP address ranges in Shorewall configuration file entries; IP address
ranges have the syntax <<emphasis>low IP
address</emphasis>>-<<emphasis>high IP address</emphasis>>.
Example: 192.168.1.5-192.168.1.12.</para>
<para>To see if your kernel and iptables have the required support, use
the <command>shorewall show capabilities</command> command:</para>
<programlisting>>~ <command>shorewall show capabilities</command>
...
Shorewall has detected the following iptables/netfilter capabilities:
NAT: Available
Packet Mangling: Available
Multi-port Match: Available
Connection Tracking Match: Available
Packet Type Match: Not available
Policy Match: Available
Physdev Match: Available
<emphasis role="bold">IP range Match: Available <--------------
</emphasis></programlisting>
</section>
<section id="Ports">
<title>Protocol Number/Names and Port Numbers/Service Names</title>
<para>Unless otherwise specified, when giving a protocol number you can
use either an integer or a protocol name from
<filename>/etc/protocols</filename>. Similarly, when giving a port number
you can use either an integer or a service name from
<filename>/etc/services</filename>.<note>
<para>Shorewall-perl translates protocol names to protocol numbers and
service names to port numbers itself. The mapping that it uses is
contained in the Perl module
<filename>/usr/share/shorewall-perl/Shorewall/Ports.pm</filename>.
That module is built when Shorewall is installed or upgraded using the
current <filename>/etc/protocols</filename> and
<filename>/etc/services</filename> files as input (if the build
program fails, a fallback version of the module is installed).</para>
<para>To generate a new Ports.pm module:<programlisting>cp /usr/share/shorewall-perl/Shorewall/Ports.pm /usr/share/shorewall-perl/Shorewall/Ports.pm.backup
/usr/share/shorewall/buildports.pm > /usr/share/shorewall-perl/Shorewall/Ports.pm</programlisting></para>
</note></para>
</section>
<section id="Ranges">
<title>Port Ranges</title>
<para>If you need to specify a range of ports, the proper syntax is
<low port number>:<high port number>. For example, if you want
to forward the range of tcp ports 4000 through 4100 to local host
192.168.1.3, the entry in /etc/shorewall/rules is:</para>
<programlisting>#ACTION SOURCE DESTINATION PROTO DEST PORTS(S)
DNAT net loc:192.168.1.3 tcp 4000:4100</programlisting>
<para>If you omit the low port number, a value of zero is assumed; if you
omit the high port number, a value of 65535 is assumed.</para>
</section>
<section id="Portlists">
<title>Port Lists</title>
<para>In most cases where a port or port range may appear, a
comma-separated list of ports or port ranges may also be entered.
Shorewall will use the Netfilter <emphasis
role="bold">multiport</emphasis> match capability if it is available (see
the output of "<emphasis role="bold">shorewall show
capabilities</emphasis>") and if its use is appropriate.</para>
<para>Shorewall can use multiport match if:</para>
<orderedlist>
<listitem>
<para>The list contains 15 or fewer port number; and</para>
</listitem>
<listitem>
<para>There are no port ranges listed OR your iptables/kernel support
the Extended <emphasis role="bold">multiport</emphasis> match (again
see the output of "<command>shorewall show capabilities</command>").
Where the Extended <emphasis role="bold">multiport</emphasis> match is
available, each port range counts as two ports toward the maximum of
15.</para>
</listitem>
</orderedlist>
<note>
<para>Shorewall-perl requires <emphasis role="bold">multiport</emphasis>
match in order to accept port lists in Shorewall configuration files. It
further requires Extended <emphasis role="bold">multiport</emphasis>
match in order to accept port ranges in port lists. Shorewall-perl will
never break a list longer than 15 ports (with each range counting as two
ports) into smaller lists. So you must be sure that your port lists can
be handled directly by the Netfilter/iptables capabilities
available.</para>
</note>
</section>
<section id="Variables">
<title>Using Shell Variables</title>
<para>You may use the /etc/shorewall/params file to set shell variables
that you can then use in some of the other configuration files.</para>
<para>It is suggested that variable names begin with an upper case letter
to distinguish them from variables used internally within the Shorewall
programs</para>
<para>Example:</para>
<blockquote>
<programlisting> /etc/shorewall/params
NET_IF=eth0
NET_BCAST=130.252.100.255
NET_OPTIONS=routefilter,norfc1918
/etc/shorewall/interfaces record:
net $NET_IF $NET_BCAST $NET_OPTIONS
The result will be the same as if the record had been written
net eth0 130.252.100.255 routefilter,norfc1918
</programlisting>
</blockquote>
<para>Variables may be used anywhere in the other configuration
files.</para>
<para>Because the <filename>/etc/shorewall/params</filename> file is
simply sourced into the shell, you can place arbitrary shell code in the
file and it will be executed each time that the file is read. Any code
included should follow these guidelines:</para>
<orderedlist>
<listitem>
<para>The code should not have side effects, especially on other
shorewall configuration files.</para>
</listitem>
<listitem>
<para>The code should be safe to execute multiple times without
producing different results.</para>
</listitem>
<listitem>
<para>Should not depend on where the code is called from (the params
file is sourced by both /sbin/shorewall and
/usr/lib/shorewall/firewall).</para>
</listitem>
<listitem>
<para>Should not assume anything about the state of Shorewall.</para>
</listitem>
<listitem>
<para>The names of any functions or variables declared should begin
with an upper case letter.</para>
</listitem>
<listitem>
<para>The <filename>/etc/shorewall/params</filename> file is processed
by the compiler at compile-time and by the compiled script at
run-time. Beginning with Shorewall 3.2.9 and 3.4.0 RC2, if you have
set EXPORTPARAMS=No in <filename>shorewall.conf</filename>, then the
<filename><filename>params</filename></filename> file is only
processed by the compiler; it is not run by the compiled
script.</para>
</listitem>
<listitem>
<para>If you are using <ulink
url="CompiledPrograms.html%23Lite">Shorewall Lite</ulink> and if the
<filename>params</filename> script needs to set shell variables based
on the configuration of the firewall system, you can use this
trick:</para>
<programlisting>EXT_IP=$(ssh root@firewall "/sbin/shorewall-lite call find_first_interface_address eth0")</programlisting>
<para>The <command>shorewall-lite call</command> command allows you to
to call interactively any Shorewall function that you can call in an
extension script.</para>
</listitem>
</orderedlist>
</section>
<section id="MAC">
<title>Using MAC Addresses</title>
<para>Media Access Control (MAC) addresses can be used to specify packet
source in several of the configuration files. In order to control traffic
to/from a host by its MAC address, the host must be on the same network as
the firewall.</para>
<para>To use this feature, your kernel must have MAC Address Match support
(CONFIG_IP_NF_MATCH_MAC) included.</para>
<para>MAC addresses are 48 bits wide and each Ethernet Controller has a
unique MAC address.</para>
<para>In GNU/Linux, MAC addresses are usually written as a series of 6 hex
numbers separated by colons.</para>
<example id="mac">
<title>MAC Address of an Ethernet Controller</title>
<programlisting> [root@gateway root]# <command>ifconfig eth0</command>
eth0 Link encap:Ethernet HWaddr <emphasis
role="bold">02:00:08:E3:FA:55</emphasis>
inet addr:206.124.146.176 Bcast:206.124.146.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:2398102 errors:0 dropped:0 overruns:0 frame:0
TX packets:3044698 errors:0 dropped:0 overruns:0 carrier:0
collisions:30394 txqueuelen:100
RX bytes:419871805 (400.4 Mb) TX bytes:1659782221 (1582.8 Mb)
Interrupt:11 Base address:0x1800
</programlisting>
</example>
<para>Because Shorewall uses colons as a separator for address fields,
Shorewall requires MAC addresses to be written in another way. In
Shorewall, MAC addresses begin with a tilde (<quote>~</quote>) and consist
of 6 hex numbers separated by hyphens. In Shorewall, the MAC address in
the example above would be written <emphasis
role="bold">~02-00-08-E3-FA-55</emphasis>.</para>
<note>
<para>It is not necessary to use the special Shorewall notation in the
<filename><ulink
url="MAC_Validation.html">/etc/shorewall/maclist</ulink></filename>
file.</para>
</note>
</section>
<section id="Levels">
<title>Shorewall Configurations</title>
<para>Shorewall allows you to have configuration directories other than
<filename class="directory">/etc/shorewall</filename>. The shorewall
check, start and restart commands allow you to specify an alternate
configuration directory and Shorewall will use the files in the alternate
directory rather than the corresponding files in /etc/shorewall. The
alternate directory need not contain a complete configuration; those files
not in the alternate directory will be read from <filename
class="directory">/etc/shorewall</filename>.</para>
<para>This facility permits you to easily create a test or temporary
configuration by</para>
<orderedlist>
<listitem>
<para>copying the files that need modification from /etc/shorewall to
a separate directory;</para>
</listitem>
<listitem>
<para>modify those files in the separate directory; and</para>
</listitem>
<listitem>
<para>specifying the separate directory in a <command>shorewall
start</command> or <command>shorewall restart</command> command (e.g.,
<command>shorewall restart /etc/testconfig</command> )</para>
</listitem>
</orderedlist>
</section>
<section id="Save">
<title>Saved Configurations</title>
<para>Shorewall allows you to <firstterm>save</firstterm> the
currently-running configuration in a form that permits it to be
re-installed quickly. When you save the configuration using the
<command>shorewall save</command> command, the running configuration is
saved in a file in the <filename
class="directory">/var/lib/shorewall</filename> directory. The default
name of that file is <filename>/var/lib/shorewall/restore</filename> but
you can specify a different name as part of the command. For example, the
command <command>shorewall save standard</command> will save the running
configuration in <filename>/var/lib/shorewall/standard</filename>. A saved
configuration is re-installed using the <command>shorewall
restore</command> command. Again, that command normally will restore the
configuration saved in <filename>/var/lib/shorewall/restore</filename> but
as with the <command>save</command> command, you can specify a different
file name in the command. For example, <command>shorewall restore
standard</command> will re-install the configuration saved in
<filename>/var/lib/shorewall/standard</filename>. By permitting you to
save different configurations under different names, Shorewall provides a
means for quickly switching between these different saved
configurations.</para>
<para>As mentioned above, the default configuration is called 'restore'
but like most things in Shorewall, that default can be changed. The
default name is specified using the <emphasis
role="bold">RESTOREFILE</emphasis> option in
<filename>/etc/shorewall/shorewall.conf</filename>.</para>
<warning>
<para>The default saved configuration is used by Shorewall in a number
of ways besides in the <command>restore</command> command; to avoid
surprises, I recommend that you read the <ulink
url="starting_and_stopping_shorewall.htm#Saved">Shorewall Operations
documentation section about saved configurations</ulink> before creating
one.</para>
</warning>
</section>
</article>