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<h1 align="center"><font color="#ffffff">MAC Verification</font><br>
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Beginning with Shorewall version 1.3.10, 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>You must have the iproute package (ip utility) installed to use MAC
Verification and 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:</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>
<pre> #ZONE INTERFACE BROADCAST OPTIONS<br> net eth0 206.124.146.255 norfc1918,filterping,dhcp,blacklist<br> loc eth2 192.168.1.255 dhcp,filterping,maclist<br> dmz eth1 192.168.2.255 filterping<br> net eth3 206.124.146.255 filterping,blacklist<br> - texas 192.168.9.255 filterping<br> loc ppp+ - filterping<br></pre>
<b>/etc/shorewall/maclist:</b><br>
<pre> #INTERFACE MAC IP ADDRESSES (Optional)<br> eth2 00:A0:CC:63:66:89 192.168.1.3 #Wookie<br> eth2 00:10:B5:EC:FD:0B 192.168.1.4 #Tarry<br> eth2 00:A0:CC:DB:31:C4 192.168.1.5 #Ursa<br> eth2 00:A0:CC:DB:31:C4 192.168.1.128/26 #PPTP Clients to server on Ursa<br> eth2 00:06:25:aa:a8:0f 192.168.1.7 #Eastept1 (Wireless)<br> eth2 00:04:5A:0E:85:B9 192.168.1.250 #Wap<br></pre>
As shown above, I use MAC Verification on <a href="myfiles.htm">my
local zone</a>.<br>
<h3>Example 2: Router in Local Zone</h3>
Suppose now that I add a second ethernet segment to my local zone and
gateway that segment via a router with MAC address 00:06:43:45:C6:15 and
IP address 192.168.1.253. Hosts in the second segment have IP addresses
in the subnet 192.168.2.0/24. I would add the following entry to my /etc/shorewall/maclist
file:<br>
<pre> eth2 00:06:43:45:C6:15 192.168.1.253,192.168.2.0/24<br></pre>
This entry accomodates traffic from the router itself (192.168.1.253)
and from the second LAN segment (192.168.2.0/24). Remember that all traffic
being sent to my firewall from the 192.168.2.0/24 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 1/7/2002 - <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>
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