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      <h1 align="center"><font color="#ffffff">Shorewall FAQs</font></h1>
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<p align="left"><b>1. </b><a href="#faq1"> I want to <b>forward</b> UDP <b>
       port</b> 7777 to my my personal PC with IP address 192.168.1.5. I've
  looked     everywhere and can't find <b>how to do it</b>.</a></p>
                           
<p align="left"><b>1a. </b><a href="#faq1a">Ok -- I followed those instructions 
       but it doesn't work.<br>
    </a></p>
                           
<p align="left"><b>1b. </b><a href="#faq1b">I'm still having problems with
  port forwarding</a></p>
       
<p align="left"><b>2.</b> <a href="#faq2">I <b>port forward</b> www requests 
      to www.mydomain.com (IP 130.151.100.69) to system 192.168.1.5 in my 
local      network. <b>External clients can browse</b> http://www.mydomain.com 
but    <b>internal  clients can't</b>.</a></p>
                           
<p align="left"><b>2a. </b><a href="#faq3">I have a zone "Z" with an RFC1918 
       subnet and I use <b>static NAT</b> to assign non-RFC1918 addresses 
to   hosts   in  Z. Hosts in Z cannot communicate with each other using their 
  external    (non-RFC1918 addresses) so they <b>can't access each other using
  their DNS   names.</b></a></p>
                            
<p align="left"><b>3. </b><a href="#faq3">I want to use <b>Netmeeting/MSN 
      Messenger </b>with  Shorewall. What do I do?</a></p>
                           
<p align="left"><b>4. </b><a href="#faq4">I just used an online port scanner 
      to  check my firewall and it shows <b>some ports as 'closed' rather 
than     'blocked'.</b>  Why?</a></p>
                           
<p align="left"><b>4a. </b><a href="#faq4a">I just ran an <b>nmap UDP scan</b> 
       of my firewall and it showed 100s of ports as open!!!!</a></p>
                           
<p align="left"><b>5. </b><a href="#faq5">I've installed Shorewall and now 
      I <b> can't ping</b> through the firewall</a></p>
                            
<p align="left"><b>6. </b><a href="#faq6">Where are the <b>log messages</b> 
       written and  how do I <b>change the destination</b>?</a></p>
                            
<p align="left"><b>6a. </b><a href="#faq6a">Are there any <b>log parsers</b> 
       that work with Shorewall?</a></p>
                            
<p align="left"><b>7. </b><a href="#faq7">When I stop Shorewall <b>using 
'shorewall stop', I can't connect to anything</b>. Why doesn't that command 
       work?</a></p>
                            
<p align="left"><b>8. </b><a href="#faq8">When I try to <b>start Shorewall 
      on RedHat 7.x</b>, I get messages about insmod failing -- what's wrong?</a></p>
                            
<p align="left"><b>9. </b><a href="FAQ.htm#faq9">Why can't Shorewall <b>detect 
      my  interfaces </b>properly?</a></p>
                                   
<p align="left"><b>10. </b><a href="#faq10">What <b>distributions</b> does 
      it  work with?</a></p>
                            
<p align="left"><b>11. </b><a href="#faq18">What <b>features</b> does it 
support?</a></p>
                            
<p align="left"><b>12. </b><a href="#faq12">Why isn't there a <b>GUI</b></a></p>
                            
<p align="left"><b>13. </b><a href="#faq13">Why do you call it <b>"Shorewall"?</b></a></p>
                           
<p align="left"><b>14. </b><a href="#faq14">I'm connected via a cable modem 
      and it has an internel  web server that allows me to configure/monitor 
   it   but as expected if I enable <b> rfc1918 blocking</b> for my eth0 interface,
      it also blocks the <b>cable modems  web server</b></a>.</p>
                           
<p align="left"><b>14a. </b><a href="#faq14a">Even though it assigns public 
      IP  addresses, my ISP's DHCP server has an RFC 1918 address. If I enable 
     RFC 1918  filtering on my external interface, <b>my DHCP client cannot 
  renew   its lease</b>.</a></p>
                            
<p align="left"><b>15. </b><a href="#faq15"><b>My local systems can't see 
      out to  the net</b></a></p>
                            
<p align="left"><b>16. </b><a href="#faq16">Shorewall is writing <b>log messages 
       all over my console</b> making it unusable!<br>
         </a></p>
                      <b>17</b>. <a href="#faq17">How do I find out <b>why
 this   is</b> getting  <b>logged?</b></a><br>
     <br>
     <b>18.</b> <a href="#faq18">Is there any way to use <b>aliased ip addresses</b> 
  with Shorewall, and maintain separate rulesets for different IPs?</a><br>
 <br>
 <b>19. </b><a href="#faq19">I have added <b>entries to /etc/shorewall/tcrules</b>
but they <b>don't </b>seem to <b>do anything</b>. Why?</a><br>
<br>
<b>20.<a href="#faq20"> </a></b><a href="#faq20">I have just set up a server.
<b>Do I have to change Shorewall to allow access to my server from the internet?</b><br>
</a> 
<hr>              
<h4 align="left"><a name="faq1"></a>1. I want to forward UDP port 7777 to 
      my my personal PC with IP address 192.168.1.5. I've looked everywhere 
  and    can't find how to do it.</h4>
                           
<p align="left"><b>Answer: </b>The <a
 href="Documentation.htm#PortForward"> first example</a> in the <a
 href="Documentation.htm#Rules">rules file documentation</a> shows how to 
      do port forwarding under Shorewall. The format of a port-forwarding 
rule to a local system is as   follows:</p>
                           
<blockquote>                                          
  <table border="1" cellpadding="2" style="border-collapse: collapse;"
 id="AutoNumber1">
                  <tbody>
                   <tr>
                    <td><u><b>ACTION</b></u></td>
                    <td><u><b>SOURCE</b></u></td>
                    <td><u><b>DESTINATION</b></u></td>
                    <td><u><b>PROTOCOL</b></u></td>
                    <td><u><b>PORT</b></u></td>
                    <td><u><b>SOURCE PORT</b></u></td>
                    <td><u><b>ORIG. DEST.</b></u></td>
                  </tr>
                  <tr>
                    <td>DNAT</td>
                    <td>net</td>
                    <td>loc:<i>&lt;local IP address&gt;</i>[:<i>&lt;local 
port</i>&gt;]</td>
                    <td><i>&lt;protocol&gt;</i></td>
                    <td><i>&lt;port #&gt;</i></td>
                    <td> <br>
                  </td>
                    <td> <br>
                  </td>
                  </tr>
                                                                        
        
    </tbody>                                       
  </table>
              </blockquote>
                           
<p align="left">So to forward UDP port 7777 to internal system 192.168.1.5, 
      the rule is:</p>
                           
<blockquote>                                          
  <table border="1" cellpadding="2" style="border-collapse: collapse;"
 id="AutoNumber1">
                  <tbody>
                   <tr>
                    <td><u><b>ACTION</b></u></td>
                    <td><u><b>SOURCE</b></u></td>
                    <td><u><b>DESTINATION</b></u></td>
                    <td><u><b>PROTOCOL</b></u></td>
                    <td><u><b>PORT</b></u></td>
                    <td><u><b>SOURCE PORT</b></u></td>
                    <td><u><b>ORIG. DEST.</b></u></td>
                  </tr>
                  <tr>
                    <td>DNAT</td>
                    <td>net</td>
                    <td>loc:192.168.1.5</td>
                    <td>udp</td>
                    <td>7777</td>
                    <td> <br>
                  </td>
                    <td> <br>
                  </td>
                  </tr>
                                                                        
        
    </tbody>                                       
  </table>
              </blockquote>
                           
<div align="left">              
<pre align="left"><font face="Courier">     DNAT net loc:192.168.1.5 udp 7777</font></pre>
              </div>
                           
<p align="left">If you want to forward requests directed to a particular
address ( <i>&lt;external IP&gt;</i> ) on your firewall to an internal system:</p>
                           
<blockquote>                                          
  <table border="1" cellpadding="2" style="border-collapse: collapse;"
 id="AutoNumber1">
                  <tbody>
                   <tr>
                    <td><u><b>ACTION</b></u></td>
                    <td><u><b>SOURCE</b></u></td>
                    <td><u><b>DESTINATION</b></u></td>
                    <td><u><b>PROTOCOL</b></u></td>
                    <td><u><b>PORT</b></u></td>
                    <td><u><b>SOURCE PORT</b></u></td>
                    <td><u><b>ORIG. DEST.</b></u></td>
                  </tr>
                  <tr>
                    <td>DNAT</td>
                    <td>net</td>
                    <td>loc:<i>&lt;local IP address&gt;</i>[:<i>&lt;local 
port</i>&gt;]</td>
                    <td><i>&lt;protocol&gt;</i></td>
                    <td><i>&lt;port #&gt;</i></td>
                    <td>-</td>
                    <td><i>&lt;external IP&gt;</i></td>
                  </tr>
                                                                        
        
    </tbody>                                       
  </table>
              </blockquote>
                           
<h4 align="left"><a name="faq1a"></a>1a. Ok -- I followed those instructions 
      but  it doesn't work</h4>
                           
<p align="left"><b>Answer: </b>That is usually the result of one of two things:</p>
                           
<ul>
                <li>You are trying to test from inside your firewall (no, 
that    won't    work -- see <a href="#faq2">FAQ #2</a>).</li>
                <li>You have a more basic problem with your local system
such   as  an   incorrect default gateway configured (it should be set to
the IP   address    of your  firewall's internal interface).</li>
                           
</ul>
                           
<h4 align="left"><a name="faq1b"></a>1b. I'm still having problems with port
  forwarding</h4>
    <b>Answer: </b>To further diagnose this problem:<br>
       
<ul>
      <li>As root, type "iptables -t nat -Z". This clears the NetFilter counters
  in the nat table.</li>
      <li>Try to connect to the redirected port from an external host.</li>
      <li>As root type "shorewall show nat"</li>
      <li>Locate the appropriate DNAT rule. It will be in a chain called
    <i>zone</i>_dnat   where <i>zone</i> is the zone that includes the server
('loc' in the above   examples).</li>
      <li>Is the packet count in the first column non-zero? If so, the connection
  request is reaching the firewall and is being redirected to the server.
In  this case, the problem is usually a missing or incorrect default gateway
 setting on the server (the server's default gateway should be the IP address
 of the firewall's interface to the server).</li>
      <li>If the packet count is zero:</li>
               
  <ul>
        <li>the connection request is not reaching your server (possibly
it  is being blocked by your ISP); or</li>
        <li>you are trying to connect to a secondary IP address on your firewall
  and your rule is only redirecting the primary IP address (You need to specify
  the secondary IP address in the "ORIG. DEST." column in your DNAT rule);
 or</li>
        <li>your DNAT rule doesn't match the connection request in some other
  way. In that case, you may have to use a packet sniffer such as tcpdump
or  ethereal to further diagnose the problem.<br>
        </li>
               
  </ul>
       
</ul>
       
<h4 align="left"><a name="faq2"></a>2. I port forward www requests to www.mydomain.com 
      (IP 130.151.100.69) to system 192.168.1.5 in my local network. External 
    clients  can browse http://www.mydomain.com but internal clients can't.</h4>
                           
<p align="left"><b>Answer: </b>I have two objections to this setup.</p>
                           
<ul>
                <li>Having an internet-accessible server in your local network
       is  like raising foxes in the corner of your hen house. If the server 
   is      compromised, there's nothing between that server and your other 
 internal        systems. For the cost of another NIC and a cross-over cable, 
 you can   put      your server in a DMZ such that it is isolated from your 
 local systems    -     assuming that the Server can be located near the Firewall,
  of course    :-)</li>
                <li>The accessibility problem is best solved using    <a
 href="shorewall_setup_guide.htm#DNS">Bind Version     9 "views"</a> (or using
a separate DNS server for local clients) such that www.mydomain.com resolves
to 130.141.100.69     externally and 192.168.1.5 internally. That's what
I do here at     shorewall.net for my local systems that use static NAT.</li>
                           
</ul>
                           
<p align="left">If you insist on an IP solution to the accessibility problem 
       rather than a DNS solution, then assuming that your external interface 
    is  eth0  and your internal interface is eth1  and that eth1 has IP address 
    192.168.1.254  with subnet 192.168.1.0/24, do the following:</p>
                           
<p align="left">a) In /etc/shorewall/interfaces, specify "multi" as an option 
       for eth1 (No longer required as of Shorewall version 1.3.9).</p>
                           
<div align="left">              
<p align="left">b) In /etc/shorewall/rules, add:</p>
             </div>
                           
<div align="left">              
<blockquote>                                          
  <table border="1" cellpadding="2" style="border-collapse: collapse;"
 id="AutoNumber1">
                  <tbody>
                   <tr>
                    <td><u><b>ACTION</b></u></td>
                    <td><u><b>SOURCE</b></u></td>
                    <td><u><b>DESTINATION</b></u></td>
                    <td><u><b>PROTOCOL</b></u></td>
                    <td><u><b>PORT</b></u></td>
                    <td><u><b>SOURCE PORT</b></u></td>
                    <td><u><b>ORIG. DEST.</b></u></td>
                  </tr>
                  <tr>
                    <td>DNAT</td>
                    <td>loc:192.168.1.0/24</td>
                    <td>loc:192.168.1.5</td>
                    <td>tcp</td>
                    <td>www</td>
                    <td>-</td>
                    <td>130.151.100.69:192.168.1.254</td>
                  </tr>
                                                                        
        
    </tbody>                                       
  </table>
              </blockquote>
              </div>
                           
<div align="left">              
<pre align="left">     <font face="Courier">DNAT    loc:192.168.1.0/24    loc:192.168.1.5    tcp    www    -    130.151.100.69:192.168.1.254</font></pre>
              </div>
                           
<div align="left">              
<p align="left">That rule only works of course if you have a static external 
      IP  address. If you  have a dynamic IP address and are running Shorewall 
     1.3.4 or later then include this in  /etc/shorewall/params:</p>
             </div>
                           
<div align="left">              
<pre>     ETH0_IP=`find_interface_address eth0`</pre>
              </div>
                           
<div align="left">              
<p align="left">and make your DNAT rule:</p>
             </div>
                           
<div align="left">              
<blockquote>                                          
  <table border="1" cellpadding="2" style="border-collapse: collapse;"
 id="AutoNumber1">
                  <tbody>
                   <tr>
                    <td><u><b>ACTION</b></u></td>
                    <td><u><b>SOURCE</b></u></td>
                    <td><u><b>DESTINATION</b></u></td>
                    <td><u><b>PROTOCOL</b></u></td>
                    <td><u><b>PORT</b></u></td>
                    <td><u><b>SOURCE PORT</b></u></td>
                    <td><u><b>ORIG. DEST.</b></u></td>
                  </tr>
                  <tr>
                    <td>DNAT</td>
                    <td>loc:192.168.1.0/24</td>
                    <td>loc:192.168.1.5</td>
                    <td>tcp</td>
                    <td>www</td>
                    <td>-</td>
                    <td>$ETH0_IP:192.168.1.254</td>
                  </tr>
                                                                        
        
    </tbody>                                       
  </table>
              </blockquote>
              </div>
                           
<div align="left">              
<p align="left">Using this technique, you will want to configure your DHCP/PPPoE 
       client to automatically restart Shorewall each time that you get a 
new    IP   address.</p>
             </div>
                           
<h4 align="left"><a name="faq2a"></a>2a. I have a zone "Z" with an RFC1918 
      subnet and I use static NAT to assign non-RFC1918 addresses to hosts 
 in   Z.  Hosts in Z cannot communicate with each other using their external 
 (non-RFC1918     addresses) so they can't access each other using their DNS
 names.</h4>
                           
<p align="left"><b>Answer: </b>This is another problem that is best solved 
      using Bind Version 9 "views". It allows both external and internal clients
      to access a NATed host using the host's DNS name.</p>
                           
<p align="left">Another good way to approach this problem is to switch from
       static NAT to Proxy ARP. That way, the hosts in Z have non-RFC1918
addresses      and can be accessed externally and internally using the same
address.  </p>
                           
<p align="left">If you don't like those solutions and prefer routing all Z-&gt;Z
traffic through your firewall then:</p>
                           
<p align="left">a) Specify "multi" on the entry for Z's interface in /etc/shorewall/interfaces
  (If you are running a Shorewall version earlier than 1.3.9).<br>
              b) Set the Z-&gt;Z policy to ACCEPT.<br>
              c) Masquerade Z to itself.<br>
              <br>
              Example:</p>
                           
<p align="left">Zone: dmz<br>
              Interface: eth2<br>
              Subnet: 192.168.2.0/24</p>
                           
<p align="left">In /etc/shorewall/interfaces:</p>
                           
<blockquote>                                          
  <table border="1" cellpadding="2" style="border-collapse: collapse;"
 id="AutoNumber2">
                  <tbody>
                   <tr>
                    <td><u><b>ZONE</b></u></td>
                    <td><u><b>INTERFACE</b></u></td>
                    <td><u><b>BROADCAST</b></u></td>
                    <td><u><b>OPTIONS</b></u></td>
                  </tr>
                  <tr>
                    <td>dmz</td>
                    <td>eth2</td>
                    <td>192.168.2.255</td>
                    <td>multi</td>
                  </tr>
                                                                        
        
    </tbody>                                       
  </table>
              </blockquote>
                           
<p align="left">In /etc/shorewall/policy:</p>
                           
<blockquote>                                          
  <table border="1" cellpadding="2" style="border-collapse: collapse;"
 id="AutoNumber3">
                  <tbody>
                   <tr>
                    <td><u><b>SOURCE </b></u></td>
                    <td><u><b>DESTINATION</b></u></td>
                    <td><u><b>POLICY</b></u></td>
                    <td><u><b>LIMIT:BURST</b></u></td>
                  </tr>
                  <tr>
                    <td>dmz</td>
                    <td>dmz</td>
                    <td>ACCEPT</td>
                    <td> <br>
                  </td>
                  </tr>
                                                                        
        
    </tbody>                                       
  </table>
              </blockquote>
                           
<div align="left">              
<pre align="left">     dmz    dmz    ACCEPT</pre>
              </div>
                           
<p align="left">In /etc/shorewall/masq:</p>
                           
<blockquote>                                          
  <table border="1" cellpadding="2" style="border-collapse: collapse;"
 id="AutoNumber3" width="369">
                  <tbody>
                   <tr>
                    <td width="93"><u><b>INTERFACE </b></u></td>
                    <td width="31"><u><b>SUBNET</b></u></td>
                    <td width="120"><u><b>ADDRESS</b></u></td>
                  </tr>
                  <tr>
                    <td width="93">eth2</td>
                    <td width="31">192.168.2.0/24</td>
                    <td width="120"> <br>
                  </td>
                  </tr>
                                                                        
        
    </tbody>                                       
  </table>
              </blockquote>
                           
<h4 align="left"><a name="faq3"></a>3. I want to use Netmeeting/MSN Messenger 
      with Shorewall. What do I do?</h4>
                           
<p align="left"><b>Answer: </b>There is an <a
 href="http://www.kfki.hu/%7Ekadlec/sw/netfilter/newnat-suite/"> H.323 connection 
      tracking/NAT module</a> that may help. Also check the Netfilter mailing 
    list  archives at <a href="http://netfilter.samba.org">http://netfilter.samba.org</a>. 
      </p>
                              
<h4 align="left"><a name="faq4"></a>4. I just used an online port scanner 
      to    check my firewall and it shows some ports as 'closed' rather than
    'blocked'.     Why?</h4>
                              
<p align="left"><b>Answer: </b>The common.def included with version 1.3.x 
      always    rejects connection requests on TCP port 113 rather than dropping 
      them. This is    necessary to prevent outgoing connection problems to
  services    that use the    'Auth' mechanism for identifying requesting 
users.  Shorewall    also rejects TCP    ports 135, 137 and 139 as well as 
UDP ports  137-139.   These are ports that are    used by Windows (Windows 
<u>can</u>  be configured   to use the DCE cell locator    on port 135). Rejecting
these  connection requests   rather than dropping them    cuts down slightly
on the amount of Windows  chatter on LAN segments connected    to the Firewall.
</p>
                              
<p align="left">If you are seeing port 80 being 'closed', that's probably 
      your    ISP preventing you from running a web server in violation of 
 your     Service    Agreement.</p>
                              
<h4 align="left"><a name="faq4a"></a>4a. I just ran an nmap UDP scan of my 
         firewall and it showed 100s of ports as open!!!!</h4>
                              
<p align="left"><b>Answer: </b>Take a deep breath and read the nmap man page 
      section about    UDP scans. If nmap gets <b>nothing</b> back from your 
   firewall   then it reports    the port as open. If you want to see which 
  UDP ports are  really open,    temporarily change your net-&gt;all policy 
  to REJECT, restart  Shorewall and do    the nmap UDP scan again.</p>
                            
<h4 align="left"><a name="faq5"></a>5. I've installed Shorewall and now I 
      can't ping through the firewall</h4>
                           
<p align="left"><b>Answer: </b>If you want your firewall to be totally open 
      for "ping": </p>
                           
<p align="left">a) Do NOT specify 'noping' on any interface in  /etc/shorewall/interfaces.<br>
              b) Copy /etc/shorewall/icmp.def to /etc/shorewall/icmpdef<br>
              c) Add the following to /etc/shorewall/icmpdef: </p>
                           
<blockquote>                                        
  <p align="left">run_iptables -A icmpdef -p ICMP --icmp-type echo-request 
      -j ACCEPT </p>
              </blockquote>
                           
<h4 align="left"><a name="faq6"></a>6. Where are the log messages written
       and  how do I change the destination?</h4>
                           
<p align="left"><b>Answer: </b>NetFilter uses the kernel's equivalent of syslog
(see "man syslog") to log messages. It always uses the LOG_KERN (kern) facility
(see "man openlog") and you get to choose the log level (again, see "man
syslog") in your <a href="Documentation.htm#Policy">policies</a>  and <a
 href="Documentation.htm#Rules">rules</a>. The destination for messaged 
logged by syslog is controlled by /etc/syslog.conf (see "man syslog.conf"). 
     When you have changed /etc/syslog.conf, be sure to restart syslogd (on 
  a  RedHat system, "service syslog restart"). </p>
                           
<p align="left">By default, older versions of Shorewall ratelimited log messages 
      through <a href="Documentation.htm#Conf">settings</a> in /etc/shorewall/shorewall.conf 
      -- If you want to log all messages, set: </p>
                           
<div align="left">              
<pre align="left">     LOGLIMIT=""<br>     LOGBURST=""</pre>
              </div>
                           
<h4 align="left"><a name="faq6a"></a>6a. Are there any log parsers that work
       with Shorewall?</h4>
                           
<p align="left"><b>Answer: </b>Here are several links that may be helpful: 
      </p>
                           
<blockquote>                                        
  <p align="left"><a
 href="http://www.shorewall.net/pub/shorewall/parsefw/"> http://www.shorewall.net/pub/shorewall/parsefw/</a><br>
              <a href="http://www.fireparse.com">http://www.fireparse.com</a><br>
              <a href="http://cert.uni-stuttgart.de/projects/fwlogwatch">http://cert.uni-stuttgart.de/projects/fwlogwatch</a><a
 href="http://www.logwatch.org"><br>
   http://www.logwatch.org</a><br>
     </p>
              </blockquote>
                           
<h4 align="left"><a name="faq7"></a>7. When I stop Shorewall using 'shorewall
       stop', I can't connect to anything. Why doesn't that command work?</h4>
                           
<p align="left">The 'stop' command is intended to place your firewall into 
      a safe state whereby only those interfaces/hosts having the 'routestopped' 
      option in /etc/shorewall/interfaces and /etc/shorewall/hosts are activated. 
      If you want to totally open up your firewall, you must use the 'shorewall 
      clear' command. </p>
                           
<h4 align="left"><a name="faq8"></a>8. When I try to start Shorewall on RedHat
       7.x, I get messages about insmod failing -- what's wrong?</h4>
                           
<p align="left"><b>Answer: </b>The output you will see looks something like 
      this:</p>
                           
<pre>     /lib/modules/2.4.17/kernel/net/ipv4/netfilter/ip_tables.o: init_module: Device or resource busy<br>     Hint: insmod errors can be caused by incorrect module parameters, including invalid IO or IRQ parameters<br>     /lib/modules/2.4.17/kernel/net/ipv4/netfilter/ip_tables.o: insmod<br>     /lib/modules/2.4.17/kernel/net/ipv4/netfilter/ip_tables.o failed<br>     /lib/modules/2.4.17/kernel/net/ipv4/netfilter/ip_tables.o: insmod ip_tables failed<br>     iptables v1.2.3: can't initialize iptables table `nat': iptables who? (do you need to insmod?)<br>     Perhaps iptables or your kernel needs to be upgraded.</pre>
                           
<p align="left">This is usually cured by the following sequence of commands: 
      </p>
                           
<div align="left">              
<pre align="left">     service ipchains stop<br>     chkconfig --delete ipchains<br>     rmmod ipchains</pre>
              </div>
                           
<div align="left">              
<p align="left">Also, be sure to check the <a href="errata.htm">errata</a> 
      for  problems concerning the version of iptables (v1.2.3) shipped with 
   RH7.2.</p>
             </div>
                           
<h4 align="left">      </h4>
                     
<h4 align="left"><a name="faq9"></a>9. Why can't Shorewall detect my    interfaces
      properly?</h4>
                              
<p align="left">I just installed Shorewall and when I issue the start command, 
         I see the following:</p>
                            
<div align="left">                
<pre>     Processing /etc/shorewall/shorewall.conf ...<br>     Processing /etc/shorewall/params ...<br>     Starting Shorewall...<br>     Loading Modules...<br>     Initializing...<br>     Determining Zones...<br>     Zones: net loc<br>     Validating interfaces file...<br>     Validating hosts file...<br>     Determining Hosts in Zones...<br><b>     Net Zone: eth0:0.0.0.0/0<br>     Local Zone: eth1:0.0.0.0/0<br></b>     Deleting user chains...<br>     Creating input Chains...<br>     ...</pre>
              </div>
                           
<div align="left">                
<p align="left">Why can't Shorewall detect my interfaces properly?</p>
             </div>
                           
<div align="left">                
<p align="left"><b>Answer: </b>The above output is perfectly normal. The Net
   zone is defined as all hosts that are connected through eth0 and the local
   zone is defined as all hosts connected through eth1</p>
             </div>
                               
<h4 align="left"><a name="faq10"></a>10. What Distributions does it work 
    with?</h4>
                               
<p align="left">Shorewall works with any GNU/Linux distribution that includes 
           the <a href="shorewall_prerequisites.htm">proper prerequisites</a>.</p>
                         
<h4 align="left">11. What Features does it have?</h4>
                               
<p align="left"><b>Answer: </b>See the <a href="shorewall_features.htm">Shorewall 
      Feature      List</a>.</p>
                         
<h4 align="left"><a name="faq12"></a>12. Why isn't there a GUI?</h4>
                               
<p align="left"><b>Answer: </b>Every time I've started to work on one, I find
myself doing      other things. I guess I just don't care enough if Shorewall
has a GUI to      invest the effort to create one myself. There are several
Shorewall GUI      projects underway however and I will publish links to
them when the authors      feel that they are ready. </p>
                         
<h4 align="left"> <a name="faq13"></a>13. Why do you call it "Shorewall"?</h4>
                               
<p align="left"><b>Answer: </b>Shorewall is a concatenation of "<u>Shore</u>line" 
      (<a href="http://www.cityofshoreline.com">the      city where I live</a>) 
      and "Fire<u>wall</u>".</p>
                         
<h4 align="left"> <a name="faq14"></a>14.  I'm connected via a cable modem 
      and it has an  internal web server that allows me to configure/monitor 
   it   but as expected if I  enable rfc1918 blocking for my eth0 interface 
  (the  internet one), it also blocks  the cable modems web server.</h4>
                               
<p align="left">Is there any way it can add a rule before the  rfc1918 blocking 
      that will let all traffic to and from the 192.168.100.1 address  of 
the    modem  in/out but still block all other rfc1918 addresses.</p>
                               
<p align="left"><b>Answer: </b>If you are running a version of Shorewall earlier
than      1.3.1, create /etc/shorewall/start and in it, place the following:</p>
                         
<div align="left">                
<pre>     run_iptables -I rfc1918 -s 192.168.100.1 -j ACCEPT</pre>
              </div>
                           
<div align="left">                
<p align="left">If you are running version 1.3.1 or later, simply add the 
         following to<a href="Documentation.htm#rfc1918"> /etc/shorewall/rfc1918</a>:</p>
             </div>
                           
<div align="left">                
<blockquote>                                            
  <table border="1" cellpadding="2" style="border-collapse: collapse;"
 id="AutoNumber3">
                    <tbody>
                   <tr>
                      <td><u><b>SUBNET </b></u></td>
                      <td><u><b>TARGET</b></u></td>
                    </tr>
                    <tr>
                      <td>192.168.100.1</td>
                      <td>RETURN</td>
                    </tr>
                                                                        
          
    </tbody>                                       
  </table>
                </blockquote>
              </div>
                             
<div align="left">                
<p align="left">Be sure that you add the entry ABOVE the entry for    192.168.0.0/16.<br>
           </p>
                     
<p align="left">Note: If you add a second IP address to your external firewall 
     interface to correspond to the modem address, you must also make an entry
     in /etc/shorewall/rfc1918 for that address. For example, if you configure
     the address 192.168.100.2 on your firewall, then you would add two entries
     to /etc/shorewall/rfc1918:  <br>
           </p>
                     
<blockquote>                                 
  <table cellpadding="2" border="1" style="border-collapse: collapse;">
               <tbody>
                 <tr>
                   <td valign="top"><u><b>SUBNET</b></u><br>
                   </td>
                   <td valign="top"><u><b>TARGET</b></u><br>
                   </td>
                 </tr>
                 <tr>
                   <td valign="top">192.168.100.1<br>
                   </td>
                   <td valign="top">RETURN<br>
                   </td>
                 </tr>
                 <tr>
                   <td valign="top">192.168.100.2<br>
                   </td>
                   <td valign="top">RETURN<br>
                   </td>
                 </tr>
                                                                 
    </tbody>                                 
  </table>
           </blockquote>
             </div>
                             
<div align="left">                
<h4 align="left"><a name="faq14a"></a>14a. Even though it assigns public IP
   addresses, my ISP's DHCP server has an RFC 1918 address. If I enable RFC
1918    filtering on my external interface, my DHCP client cannot renew its
lease.</h4>
              </div>
                             
<div align="left">                
<p align="left">The solution is the same as FAQ 14 above. Simply substitute 
         the IP address of your ISPs DHCP server.</p>
             </div>
                           
<h4 align="left"><a name="faq15"></a>15. My local systems can't see out to 
      the  net</h4>
                            
<p align="left"><b>Answer: </b>Every time I read "systems can't see out to 
      the net", I wonder  where the poster bought computers with eyes and 
what     those computers will "see"  when things are working properly. That 
aside,     the most common causes of this  problem are:</p>
                            
<ol>
                <li>                                                    
           
    <p align="left">The default gateway on each local system isn't set to 
      the    IP address of the local firewall interface.</p>
                 </li>
                <li>                                                    
           
    <p align="left">The entry for the local network in the /etc/shorewall/masq 
         file is wrong or missing.</p>
                 </li>
                <li>                                                    
           
    <p align="left">The DNS settings on the local systems are wrong or the 
         user is running a DNS server on the firewall and hasn't enabled UDP
   and   TCP    port 53 from the firewall to the internet.</p>
                 </li>
                           
</ol>
                           
<h4 align="left"><a name="faq16"></a>16. Shorewall is writing log messages 
      all  over my console making it unusable!</h4>
                              
<p align="left"><b>Answer: </b>"man dmesg" -- add a suitable 'dmesg' command 
      to your startup    scripts or place it in /etc/shorewall/start. Under 
  RedHat,    the max log level    that is sent to the console is specified 
 in /etc/sysconfig/init    in the    LOGLEVEL variable.<br>
         </p>
                 
<h4><a name="faq17"></a>17. How do I find out why this is getting logged?</h4>
         <b>Answer: </b>Logging occurs out of a number of chains (as indicated
   in  the log message) in Shorewall:<br>
                 
<ol>
           <li><b>man1918 - </b>The destination address is listed in /etc/shorewall/rfc1918 
    with a <b>logdrop </b>target -- see <a
 href="Documentation.htm#rfc1918">/etc/shorewall/rfc1918.</a></li>
           <li><b>rfc1918</b> - The source address is listed in /etc/shorewall/rfc1918 
    with a <b>logdrop </b>target�-- see <a
 href="Documentation.htm#rfc1918">/etc/shorewall/rfc1918.</a></li>
          <li><b>all2&lt;zone&gt;</b>, <b>&lt;zone&gt;2all</b> or <b>all2all
      </b>-  You have a<a href="Documentation.htm#Policy"> policy</a> that
 specifies a  log level and this packet is being logged under that policy.
 If you intend  to ACCEPT this traffic then you need a  <a
 href="Documentation.htm#Rules">rule</a> to that effect.<br>
          </li>
           <li><b>&lt;zone1&gt;2&lt;zone2&gt; </b>- Either you have a<a
 href="Documentation.htm#Policy"> policy</a> for <b>&lt;zone1&gt; </b>to 
   <b>&lt;zone2&gt;</b> that specifies a log level and this packet is being 
   logged under that policy or this packet matches  a <a
 href="Documentation.htm#Rules">rule</a> that includes a log level.</li>
    <li><b>&lt;interface&gt;_mac</b> - The packet is being logged under the
     <b>maclist</b> <a href="Documentation.htm#Interfaces">interface option</a>.<br>
    </li>
           <li><b>logpkt</b> - The packet is being logged under the <b>logunclean</b> 
        <a href="Documentation.htm#Interfaces">interface option</a>.</li>
           <li><b>badpkt </b>- The packet is being logged under the <b>dropunclean</b> 
        <a href="Documentation.htm#Interfaces">interface option</a> as specified 
    in the <b>LOGUNCLEAN </b>setting in <a href="Documentation.htm#Conf">/etc/shorewall/shorewall.conf</a>.</li>
           <li><b>blacklst</b> - The packet is being logged because the source
   IP  is blacklisted in the<a href="Documentation.htm#Blacklist"> /etc/shorewall/blacklist 
        </a>file.</li>
           <li><b>newnotsyn </b>- The packet is being logged because it is
 a  TCP   packet that is not part of any current connection yet it is not
a syn  packet.   Options affecting the logging of such packets include <b>NEWNOTSYN
      </b>and       <b>LOGNEWNOTSYN </b>in     <a
 href="Documentation.htm#Conf">/etc/shorewall/shorewall.conf.</a></li>
          <li><b>INPUT</b> or <b>FORWARD</b> - The packet has a source IP 
address    that isn't in any of your defined zones ("shorewall check" and 
look at the   printed zone definitions) or the chain is FORWARD and the destination
 IP  isn't in any of your defined zones.</li>
                 
</ol>
         
<h4><a name="faq18"></a>18. Is there any way to use <b>aliased ip addresses</b> 
  with Shorewall, and maintain separate rulesets for different IPs?</h4>
     <b>Answer: </b>Yes. You simply use the IP address in your rules (or
if  you  use NAT, use the local IP address in your rules). <b>Note:</b> The 
":n"  notation  (e.g., eth0:0) is deprecated and will disappear eventually. 
Neither   iproute  (ip and tc) nor iptables supports that notation so neither 
does   Shorewall.  <br>
     <br>
     <b>Example 1:</b><br>
     <br>
     /etc/shorewall/rules     
<pre wrap=""><span class="moz-txt-citetags"></span>     # Accept AUTH but only on address 192.0.2.125<br><span
 class="moz-txt-citetags"></span><br><span class="moz-txt-citetags"></span>     ACCEPT	net	fw:192.0.2.125	tcp	auth<br><span
 class="moz-txt-citetags"></span></pre>
     <span class="moz-txt-citetags"></span><b>Example 2 (NAT):</b><br>
     <br>
     <span class="moz-txt-citetags"></span>/etc/shorewall/nat<br>
         
<pre wrap=""><span class="moz-txt-citetags"></span><span
 class="moz-txt-citetags"></span>     192.0.2.126	eth0	10.1.1.126</pre>
     /etc/shorewall/rules     
<pre wrap=""><span class="moz-txt-citetags"></span>     # Accept HTTP on 192.0.2.126 (a.k.a. 10.1.1.126)<br><span
 class="moz-txt-citetags"></span><br>     <span class="moz-txt-citetags"></span>ACCEPT	net	loc:10.1.1.126	tcp	www<span
 class="moz-txt-citetags"></span><br></pre>
  <b>Example 3 (DNAT):<br>
  </b>  
<pre>     # Forward SMTP on external address 192.0.2.127 to local system 10.1.1.127<br><br>     DNAT	net	loc:10.1.1.127	tcp	smtp	-	192.0.2.127<br></pre>
 
<h4><b><a name="faq19"></a>19. </b>I have added entries to /etc/shorewall/tcrules 
but they don't seem to do anything. Why?</h4>
 You probably haven't set TC_ENABLED=Yes in /etc/shorewall/shorewall.conf 
so the contents of the tcrules file are simply being ignored.<br>
<h4><a name="faq20"></a><b>20. </b>I have just set up a server. <b>Do I have
to change Shorewall to allow access to my server from the internet?</b><br>
</h4>
Yes. Consult the <a href="shorewall_quickstart_guide.htm">QuickStart guide</a>
that you used during your initial setup for information about how to set
up rules for your server.<br>
<br>
                              
<div align="left">     </div>
  <font size="2">Last updated 11/24/2002 - <a href="support.htm">Tom Eastep</a></font> 
                          
<p><font face="Trebuchet MS"><a href="copyright.htm"><font size="2">Copyright</font> 
       � <font size="2">2001, 2002 Thomas M. Eastep.</font></a></font><br>
     <br>
    </p>
    <br>
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