forked from extern/shorewall_code
b7b4f6d2e8
git-svn-id: https://shorewall.svn.sourceforge.net/svnroot/shorewall/trunk@192 fbd18981-670d-0410-9b5c-8dc0c1a9a2bb
571 lines
25 KiB
HTML
571 lines
25 KiB
HTML
<html>
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<head>
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<meta http-equiv="Content-Language" content="en-us">
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<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
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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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<title>Shorewall FAQ</title>
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<meta name="Microsoft Theme" content="boldstri 011, default">
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</head>
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<body>
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<h1 align="center">Shorewall FAQs</h1>
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<h2 align="left">About Shorewall</h2>
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<blockquote>
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<p align="left"><a href="#faq13">Why do you call it "Shorewall"?</a></p>
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<p align="left"><a href="#faq10">What distributions does it work with?</a></p>
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<p align="left"><a href="shorewall_features.htm">What features does it support?</a></p>
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<p align="left"><a href="#faq12">Why isn't there a GUI?</a></p>
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</blockquote>
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<h2 align="left">Filtering</h2>
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<blockquote>
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<p align="left"><a href="#faq14">I'm connected via a cable modem and it has an
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internel web server that allows me to configure/monitor it but as expected if I
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enable rfc1918 blocking for my eth0 interface, it also blocks the cable modems
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web server</a>.</p>
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<p align="left"><a href="#faq14a">Even though it assigns public IP addresses, my
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ISP's DHCP server has an RFC 1918 address. If I enable RFC 1918 filtering on my
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external interface, my DHCP client cannot renew its lease.</a></p>
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<p align="left"><a href="#faq4">I just used an online port scanner to check my
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firewall and it shows some ports as 'closed' rather than 'blocked'. Why?</a></p>
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<p align="left"><a href="#faq4a">I just ran an nmap UDP scan of my firewall and
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it showed 100s of ports as open!!!!</a></p>
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</blockquote>
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<h2 align="left">Port Forwarding</h2>
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<blockquote>
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<p align="left"><a href="#faq1">I want to forward UDP port 7777 to my my personal PC with IP
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address 192.168.1.5. I've looked everywhere and can't find how to do it.</a></p>
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<p align="left"><a href="#faq1a">Ok -- I followed those instructions but it
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doesn't work.</a></p>
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<p align="left"><a href="#faq2">I port forward www requests to www.mydomain.com (IP
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130.151.100.69) to system 192.168.1.5 in my local network. External clients can browse
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http://www.mydomain.com but internal clients can't.</a></p>
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<p align="left"><a href="#faq3">I have a zone "Z" with an RFC1918 subnet and I
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use static NAT to assign non-RFC1918 addresses to hosts in Z. Hosts in Z cannot
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communicate with each other using their external (non-RFC1918 addresses) so they
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can't access each other using their DNS names.</a></p>
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</blockquote>
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<h2 align="left">Applications</h2>
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<blockquote>
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<p align="left"><a href="#faq3">I want to use Netmeeting with Shorewall. What do I do?</a></p>
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</blockquote>
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<h2 align="left">Connection Problems</h2>
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<blockquote>
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<p align="left"><a href="#faq5">I've installed Shorewall and now I can't ping through the
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firewall</a></p>
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<p align="left"><a href="#faq15">My local systems can't see out to the net</a></p>
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</blockquote>
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<h2 align="left">Logging</h2>
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<blockquote>
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<p align="left"><a href="#faq6">Where are the log messages written and
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how do I change the destination?</a></p>
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<p align="left"><a href="#faq16">Shorewall is writing log messages all over my
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console making it unusable!</a></p>
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<p align="left"><a href="#faq6a">Are there any log parsers that work with
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Shorewall?</a></p>
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</blockquote>
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<h2 align="left">Starting and stopping the firewall</h2>
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<blockquote>
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<p align="left"><a href="#faq7">When I stop Shorewall using 'shorewall stop',
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I can't connect to anything. Why doesn't that command work?</a></p>
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<p align="left"><a href="#faq8">When I try to start Shorewall on RedHat 7.x, I
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get messages about insmod failing -- what's wrong?</a></p>
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<p align="left"><a href="#faq17">Why can't Shorewall detect my interfaces
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properly?</a></p>
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</blockquote>
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<h2 align="left">Design</h2>
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<blockquote>
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<p align="left"><a href="#faq9">Why does Shorewall only accept IP addresses as
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opposed to FQDNs?</a></p>
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</blockquote>
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<hr>
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<h4 align="left"><a name="faq1"></a>1. I want to forward UDP port 7777 to my my personal PC with IP
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address 192.168.1.5. I've looked everywhere and can't find how to do it.</h4>
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<p align="left"><b>Answer: </b>The <a href="Documentation.htm#PortForward"> first example</a> in the <a href="Documentation.htm#Rules">rules
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file documentation</a> shows how to do port forwarding under Shorewall. Assuming
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that you have a dynamic external IP address, the format of a port-forwarding
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rule to a local system is as follows:</p>
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<blockquote>
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<table border="1" cellpadding="2" style="border-collapse: collapse" id="AutoNumber1">
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<tr>
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<td><u><b>ACTION</b></u></td>
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<td><u><b>SOURCE</b></u></td>
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<td><u><b>DESTINATION</b></u></td>
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<td><u><b>PROTOCOL</b></u></td>
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<td><u><b>PORT</b></u></td>
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<td><u><b>SOURCE PORT</b></u></td>
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<td><u><b>ORIG. DEST.</b></u></td>
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</tr>
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<tr>
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<td>DNAT</td>
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<td>net</td>
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<td>loc:<i><local IP address></i>[:<i><local port</i>>]</td>
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<td><i><protocol></i></td>
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<td><i><port #></i></td>
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<td> </td>
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<td> </td>
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</tr>
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</table>
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</blockquote>
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<p align="left">So to forward UDP port 7777 to internal system 192.168.1.5, the
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rule is:</p>
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<blockquote>
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<table border="1" cellpadding="2" style="border-collapse: collapse" id="AutoNumber1">
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<tr>
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<td><u><b>ACTION</b></u></td>
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<td><u><b>SOURCE</b></u></td>
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<td><u><b>DESTINATION</b></u></td>
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<td><u><b>PROTOCOL</b></u></td>
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<td><u><b>PORT</b></u></td>
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<td><u><b>SOURCE PORT</b></u></td>
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<td><u><b>ORIG. DEST.</b></u></td>
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</tr>
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<tr>
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<td>DNAT</td>
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<td>net</td>
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<td>loc:192.168.1.5</td>
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<td>udp</td>
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<td>7777</td>
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<td> </td>
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<td> </td>
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</tr>
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</table>
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</blockquote>
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<div align="left">
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<pre align="left"><font face="Courier"> DNAT net loc:192.168.1.5 udp 7777</font></pre>
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</div>
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<p align="left">If you want to forward requests directed to a particular
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address ( <i><external IP></i> ) on your firewall to an internal system:</p>
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<blockquote>
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<table border="1" cellpadding="2" style="border-collapse: collapse" id="AutoNumber1">
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<tr>
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<td><u><b>ACTION</b></u></td>
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<td><u><b>SOURCE</b></u></td>
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<td><u><b>DESTINATION</b></u></td>
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<td><u><b>PROTOCOL</b></u></td>
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<td><u><b>PORT</b></u></td>
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<td><u><b>SOURCE PORT</b></u></td>
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<td><u><b>ORIG. DEST.</b></u></td>
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</tr>
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<tr>
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<td>DNAT</td>
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<td>net</td>
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<td>loc:<i><local IP address></i>[:<i><local port</i>>]</td>
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<td><i><protocol></i></td>
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<td><i><port #></i></td>
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<td>-</td>
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<td><i><external IP></i></td>
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</tr>
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</table>
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</blockquote>
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<h4 align="left"><a name="faq1a"></a>1a. Ok -- I followed those instructions but
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it doesn't work</h4>
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<p align="left"><b>Answer: </b>That is usually the result of one of two things:</p>
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<ul>
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<li>You are trying to test from inside your firewall (no, that
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won't work -- see <a href="#faq2">FAQ #2</a>).</li>
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<li>You have a more basic problem with your local system such as an
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incorrect default gateway configured (it should be set to the IP address of your
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firewall's internal interface).</li>
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</ul>
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<h4 align="left"><a name="faq2"></a>2. I port forward www requests to www.mydomain.com (IP
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130.151.100.69) to system 192.168.1.5 in my local network. External clients can browse
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http://www.mydomain.com but internal clients can't.</h4>
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<p align="left"><b>Answer: </b>I have two objections to this setup.</p>
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<ul>
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<li>Having an internet-accessible server in your local network
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is like raising foxes in the corner of your hen house. If the server is
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compromised, there's nothing between that server and your other internal
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systems. For the cost of another NIC and a cross-over cable, you can put
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your server in a DMZ such that it is isolated from your local systems -
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assuming that the Server can be located near the Firewall, of course :-)</li>
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<li>The accessibility problem is best solved using
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<a href="shorewall_setup_guide.htm#DNS">Bind Version
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9 "views"</a> (or using a separate DNS server for local clients) such that www.mydomain.com resolves to 130.141.100.69
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externally and 192.168.1.5 internally. That's what I do here at
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shorewall.net for my local systems that use static NAT.</li>
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</ul>
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<p align="left">If you insist on an IP solution to the accessibility problem
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rather than a DNS solution, then assuming that your external interface is eth0
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and your internal interface is eth1
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and that eth1 has IP address 192.168.1.254 with subnet 192.168.1.0/24, do the following:</p>
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<p align="left">a) In /etc/shorewall/interfaces, specify "multi" as an option
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for eth1.</p>
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<div align="left">
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<p align="left">b) In /etc/shorewall/rules, add:</div>
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<div align="left">
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<blockquote>
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<table border="1" cellpadding="2" style="border-collapse: collapse" id="AutoNumber1">
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<tr>
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<td><u><b>ACTION</b></u></td>
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<td><u><b>SOURCE</b></u></td>
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<td><u><b>DESTINATION</b></u></td>
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<td><u><b>PROTOCOL</b></u></td>
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<td><u><b>PORT</b></u></td>
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<td><u><b>SOURCE PORT</b></u></td>
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<td><u><b>ORIG. DEST.</b></u></td>
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</tr>
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<tr>
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<td>DNAT</td>
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<td>loc:192.168.1.0/24</td>
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<td>loc:192.168.1.5</td>
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<td>tcp</td>
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<td>www</td>
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<td>-</td>
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<td>130.151.100.69:192.168.1.254</td>
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</tr>
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</table>
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</blockquote>
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</div>
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<div align="left">
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<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>
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</div>
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<div align="left">
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<p align="left">That rule only works of course if you have a static external IP
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address. If you
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have a dynamic IP address and are running Shorewall 1.3.4 or later then include this in
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/etc/shorewall/params:</div>
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<div align="left">
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<pre> ETH0_IP=`find_interface_address eth0`</pre>
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</div>
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<div align="left">
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<p align="left">and make your DNAT rule:</div>
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<div align="left">
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<blockquote>
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<table border="1" cellpadding="2" style="border-collapse: collapse" id="AutoNumber1">
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<tr>
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<td><u><b>ACTION</b></u></td>
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<td><u><b>SOURCE</b></u></td>
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<td><u><b>DESTINATION</b></u></td>
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<td><u><b>PROTOCOL</b></u></td>
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<td><u><b>PORT</b></u></td>
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<td><u><b>SOURCE PORT</b></u></td>
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<td><u><b>ORIG. DEST.</b></u></td>
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</tr>
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<tr>
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<td>DNAT</td>
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<td>loc:192.168.1.0/24</td>
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<td>loc:192.168.1.5</td>
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<td>tcp</td>
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<td>www</td>
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<td>-</td>
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<td>$ETH0_IP:192.168.1.254</td>
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</tr>
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</table>
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</blockquote>
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</div>
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<div align="left">
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<p align="left">Using this technique, you will want to configure your DHCP/PPPoE
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client to automatically restart Shorewall each time that you get a new IP
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address.</div>
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<h4 align="left"><a name="faq2a"></a>2a. I have a zone "Z" with an RFC1918 subnet and I
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use static NAT to assign non-RFC1918 addresses to hosts in Z. Hosts in Z cannot
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communicate with each other using their external (non-RFC1918 addresses) so they
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can't access each other using their DNS names.</h4>
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<p align="left"><b>Answer: </b>This is another problem that is best solved using Bind Version 9
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"views". It allows both external and internal clients to access a
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NATed host using the host's DNS name.</p>
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<p align="left">Another good way to approach this problem is to switch from
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static NAT to Proxy ARP. That way, the hosts in Z have non-RFC1918 addresses and
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can be accessed externally and internally using the same address. </p>
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<p align="left">If you don't like those solutions and prefer routing all Z->Z
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traffic through your firewall then:</p>
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<p align="left">a) Specify "multi" on the entry for Z's interface in
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/etc/shorewall/interfaces.<br>
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b) Set the Z->Z policy to ACCEPT.<br>
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c) Masquerade Z to itself.<br>
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<br>
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Example:</p>
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<p align="left">Zone: dmz<br>
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Interface: eth2<br>
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Subnet: 192.168.2.0/24</p>
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<p align="left">In /etc/shorewall/interfaces:</p>
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<blockquote>
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<table border="1" cellpadding="2" style="border-collapse: collapse" id="AutoNumber2">
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<tr>
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<td><u><b>ZONE</b></u></td>
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<td><u><b>INTERFACE</b></u></td>
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<td><u><b>BROADCAST</b></u></td>
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<td><u><b>OPTIONS</b></u></td>
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</tr>
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<tr>
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<td>dmz</td>
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<td>eth2</td>
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<td>192.168.2.255</td>
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<td>multi</td>
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</tr>
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</table>
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</blockquote>
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<p align="left">In /etc/shorewall/policy:</p>
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<blockquote>
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<table border="1" cellpadding="2" style="border-collapse: collapse" id="AutoNumber3">
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<tr>
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<td><u><b>SOURCE </b></u></td>
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<td><u><b>DESTINATION</b></u></td>
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<td><u><b>POLICY</b></u></td>
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<td><u><b>LIMIT:BURST</b></u></td>
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</tr>
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<tr>
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<td>dmz</td>
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<td>dmz</td>
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<td>ACCEPT</td>
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<td> </td>
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</tr>
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</table>
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</blockquote>
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<div align="left">
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<pre align="left"> dmz dmz ACCEPT</pre>
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</div>
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<p align="left">In /etc/shorewall/masq:</p>
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<blockquote>
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<table border="1" cellpadding="2" style="border-collapse: collapse" id="AutoNumber3" width="369">
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<tr>
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<td width="93"><u><b>INTERFACE </b></u></td>
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<td width="31"><u><b>SUBNET</b></u></td>
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<td width="120"><u><b>ADDRESS</b></u></td>
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</tr>
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<tr>
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<td width="93">eth2</td>
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<td width="31">192.168.2.0/24</td>
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<td width="120"> </td>
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</tr>
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</table>
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</blockquote>
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<h4 align="left"><a name="faq3"></a>3. I want to use Netmeeting with Shorewall. What do I do?</h4>
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<p align="left"><b>Answer: </b>There is an <a href="http://www.kfki.hu/~kadlec/sw/netfilter/newnat-suite/"> H.323 connection tracking/NAT module</a> that may help.
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Also check the Netfilter mailing list archives at <a href="http://netfilter.samba.org">http://netfilter.samba.org</a>. </p>
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<h4 align="left"><a name="faq4"></a>4. I just used an online port scanner to
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check my firewall and it shows some ports as 'closed' rather than 'blocked'.
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Why?</h4>
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<p align="left"><b>Answer: </b>The common.def included with version 1.3.x always
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rejects connection requests on TCP port 113 rather than dropping them. This is
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necessary to prevent outgoing connection problems to services that use the
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'Auth' mechanism for identifying requesting users. Shorewall also rejects TCP
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ports 135, 137 and 139 as well as UDP ports 137-139. These are ports that are
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used by Windows (Windows <u>can</u> be configured to use the DCE cell locator
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on port 135). Rejecting these connection requests rather than dropping them
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cuts down slightly on the amount of Windows chatter on LAN segments connected
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to the Firewall. </p>
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<p align="left">If you are seeing port 80 being 'closed', that's probably your
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ISP preventing you from running a web server in violation of your Service
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Agreement.</p>
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<h4 align="left"><a name="faq4a"></a>4a. I just ran an nmap UDP scan of my
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firewall and it showed 100s of ports as open!!!!</h4>
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<p align="left"><b>Answer: </b>Take a deep breath and read the nmap man page section about
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UDP scans. If nmap gets <b>nothing</b> back from your firewall then it reports
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the port as open. If you want to see which UDP ports are really open,
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temporarily change your net->all policy to REJECT, restart Shorewall and do
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the nmap UDP scan again.</p>
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<h4 align="left"><a name="faq5"></a>5. I've installed Shorewall and now I can't ping through the
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firewall</h4>
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<p align="left"><b>Answer: </b>If you want your firewall to be totally open for
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"ping": </p>
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<p align="left">a) Do NOT specify 'noping' on any interface in
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/etc/shorewall/interfaces.<br>
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b) Copy /etc/shorewall/icmp.def to /etc/shorewall/icmpdef<br>
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c) Add the following to /etc/shorewall/icmpdef: </p>
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<blockquote>
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<p align="left">run_iptables -A icmpdef -p ICMP --icmp-type echo-request -j
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ACCEPT </p>
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</blockquote>
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<h4 align="left"><a name="faq6"></a>6. Where are the log messages written
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and how do I change the destination?</h4>
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<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=""
|
||
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></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
|
||
Hint: insmod errors can be caused by incorrect module parameters, including invalid IO or IRQ parameters
|
||
/lib/modules/2.4.17/kernel/net/ipv4/netfilter/ip_tables.o: insmod
|
||
/lib/modules/2.4.17/kernel/net/ipv4/netfilter/ip_tables.o failed
|
||
/lib/modules/2.4.17/kernel/net/ipv4/netfilter/ip_tables.o: insmod ip_tables failed
|
||
iptables v1.2.3: can't initialize iptables table `nat': iptables who? (do you need to insmod?)
|
||
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
|
||
chkconfig --delete ipchains
|
||
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.</div>
|
||
<h4 align="left"> <a name="faq9"></a>9. Why does Shorewall only accept IP
|
||
addresses as opposed to FQDNs?</h4><p align="left"> <b>Answer: </b>FQDNs 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 change in the DNS->IP address relationship
|
||
that occur after the firewall has started have absolutely no effect on the
|
||
firewall's ruleset.</p>
|
||
<p align="left"> I'm also trying to protect
|
||
people from themselves. If your firewall rules include FQDN's then:</p>
|
||
<ul>
|
||
<li>If your /etc/resolv.conf is wrong then your firewall won't
|
||
start.</li>
|
||
<li>If your /etc/nsswitch.conf is wrong then your firewall won't
|
||
start.</li>
|
||
<li>If your Name Server(s) is(are) down then your firewall won't
|
||
start.</li>
|
||
<li>Factors totally outside your control (your ISP's router is
|
||
down for example), can prevent your firewall from starting.</li>
|
||
</ul>
|
||
<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>.<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>.<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. <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>".<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:<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>:</div>
|
||
<div align="left">
|
||
<blockquote>
|
||
<table border="1" cellpadding="2" style="border-collapse: collapse" id="AutoNumber3">
|
||
<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>
|
||
</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.</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.</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.</p>
|
||
|
||
<h4 align="left"><a name="faq17"></a>17. 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 ...
|
||
Processing /etc/shorewall/params ...
|
||
Starting Shorewall...
|
||
Loading Modules...
|
||
Initializing...
|
||
Determining Zones...
|
||
Zones: net loc
|
||
Validating interfaces file...
|
||
Validating hosts file...
|
||
Determining Hosts in Zones...
|
||
<b> Net Zone: eth0:0.0.0.0/0
|
||
Local Zone: eth1:0.0.0.0/0
|
||
</b> Deleting user chains...
|
||
Creating input Chains...
|
||
...</pre>
|
||
</div>
|
||
<div align="left">
|
||
<p align="left">Why can't Shorewall detect my interfaces properly?</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.
|
||
</div>
|
||
|
||
<p align="left"><font size="2">Last updated
|
||
7/31/2002 - <a href="support.htm">Tom
|
||
Eastep</a></font></p>
|
||
|
||
<p><font face="Trebuchet MS"><a href="copyright.htm"><font size="2">Copyright</font>
|
||
<EFBFBD> <font size="2">2001, 2002 Thomas M. Eastep.</font></a></font></p>
|
||
|
||
</body>
|
||
|
||
</html> |