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<h1 align="center"><font color="#ffffff">MAC Verification</font><br>
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All traffic from an interface or from a subnet on an interface
can be verified to originate from a defined set of MAC addresses. Furthermore,
each MAC address may be optionally associated with one or more IP addresses.
<br>
<br>
<b>Your kernel must include MAC match support (CONFIG_IP_NF_MATCH_MAC
- module name ipt_mac.o).</b><br>
<br>
There are four components to this facility.<br>
<ol>
<li>The <b>maclist</b> interface option in <a
href="Documentation.htm#Interfaces">/etc/shorewall/interfaces</a>. When
this option is specified, all traffic arriving on the interface is subjet
to MAC verification.</li>
<li>The <b>maclist </b>option in <a
href="Documentation.htm#Hosts">/etc/shorewall/hosts</a>. When this option
is specified for a subnet, all traffic from that subnet is subject to
MAC verification.</li>
<li>The /etc/shorewall/maclist file. This file is used to associate
MAC addresses with interfaces and to optionally associate IP addresses
with MAC addresses.</li>
<li>The <b>MACLIST_DISPOSITION </b>and <b>MACLIST_LOG_LEVEL
</b>variables in <a href="Documentation.htm#Conf">/etc/shorewall/shorewall.conf.</a>
The MACLIST_DISPOSITION variable has the value DROP, REJECT or ACCEPT
and determines the disposition of connection requests that fail MAC verification.
The MACLIST_LOG_LEVEL variable gives the syslogd level at which connection
requests that fail verification are to be logged. If set the the empty
value (e.g., MACLIST_LOG_LEVEL="") then failing connection requests are
not logged.<br>
</li>
</ol>
The columns in /etc/shorewall/maclist are:<br>
<ul>
<li>INTERFACE - The name of an ethernet interface on the Shorewall
system.</li>
<li>MAC - The MAC address of a device on the ethernet segment
connected by INTERFACE. It is not necessary to use the Shorewall MAC
format in this column although you may use that format if you so choose.</li>
<li>IP Address - An optional comma-separated list of IP addresses
for the device whose MAC is listed in the MAC column.</li>
</ul>
<h3>Example 1: Here are my files (look <a href="myfiles.htm">here</a> for
details about my setup):</h3>
<b>/etc/shorewall/shorewall.conf:<br>
</b>
<pre> MACLIST_DISPOSITION=REJECT<br> MACLIST_LOG_LEVEL=info<br></pre>
<b>/etc/shorewall/interfaces:</b><br>
<blockquote>
<pre>#ZONE INTERFACE BROADCAST OPTIONS<br>net eth0 206.124.146.255 dhcp,norfc1918,routefilter,blacklist,tcpflags<br>loc eth2 192.168.1.255 dhcp<br>dmz eth1 192.168.2.255<br>WiFi eth3 192.168.3.255 dhcp,maclist<br>- texas 192.168.9.255</pre>
</blockquote>
<b>/etc/shorewall/maclist:</b><br>
<blockquote>
<pre>#INTERFACE MAC IP ADDRESSES (Optional)<br>eth3 00:A0:CC:A2:0C:A0 192.168.3.7 #Work Laptop<br>eth3 00:04:5a:fe:85:b9 192.168.3.250 #WAP11<br>eth3 00:06:25:56:33:3c 192.168.3.225,192.168.3.8 #WET11<br>eth3 00:0b:cd:C4:cc:97 192.168.3.8 #TIPPER</pre>
</blockquote>
As shown above, I use MAC Verification on my wireless zone.<br>
<br>
<b>Note: </b>While marketed as a wireless bridge, the WET11 behaves like
a wireless router with DHCP relay. When forwarding DHCP traffic, it uses the
MAC address of the host (TIPPER) but for other forwarded traffic it uses it's
own MAC address. Consequently, I list the IP addresses of both devices in
/etc/shorewall/maclist.<br>
<h3>Example 2: Router in Wireless Zone</h3>
Suppose now that I add a second wireless segment to my wireless
zone and gateway that segment via a router with MAC address 00:06:43:45:C6:15
and IP address 192.168.3.253. Hosts in the second segment have IP addresses
in the subnet 192.168.4.0/24. I would add the following entry to my /etc/shorewall/maclist
file:<br>
<pre> eth3 00:06:43:45:C6:15 192.168.3.253,192.168.4.0/24<br></pre>
This entry accomodates traffic from the router itself (192.168.3.253)
and from the second wireless segment (192.168.4.0/24). Remember that
all traffic being sent to my firewall from the 192.168.4.0/24 segment
will be forwarded by the router so that traffic's MAC address will be
that of the router (00:06:43:45:C6:15) and not that of the host sending
the traffic.
<p><font size="2"> Updated 6/30/2002 - <a href="support.htm">Tom Eastep</a>
</font></p>
<p><a href="copyright.htm"><font size="2">Copyright</font> ©
<font size="2">2001, 2002, 2003 Thomas M. Eastep.</font></a><br>
</p>
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