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Update the Troubleshooting Guide
git-svn-id: https://shorewall.svn.sourceforge.net/svnroot/shorewall/trunk@4569 fbd18981-670d-0410-9b5c-8dc0c1a9a2bb
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@ -32,37 +32,6 @@
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</legalnotice>
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</articleinfo>
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<section>
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<title>First Steps</title>
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<para>Some problems are easily solved by checking one of the resources
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described in the following sections.</para>
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<section>
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<title>Check the FAQs.</title>
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<para>Check the <ulink url="FAQ.htm">FAQs</ulink> for solutions to over
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50 common problems.</para>
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</section>
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<section>
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<title>Check the Errata</title>
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<para>Check the <ulink url="errata.htm">Shorewall Errata</ulink> to be
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sure that there isn't an update that you are missing for your version of
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the firewall.</para>
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</section>
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<section>
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<title>Try Searching the Shorewall Site and Mailing List
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Archives</title>
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<para>The <ulink url="http://shorewall.net/search.html">Site and Mailing
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List Archives search facility</ulink> can locate documents and posts
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about similar problems.</para>
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</section>
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</section>
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<section>
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<title><quote>shorewall start</quote> and <quote>shorewall restart</quote>
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Errors</title>
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@ -121,62 +90,6 @@ iptables: No chain/target/match by that name
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</example>
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</section>
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<section>
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<title>Some Things to Keep in Mind</title>
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<itemizedlist>
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<listitem>
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<para><emphasis role="bold">You cannot test your firewall from the
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inside</emphasis>. Just because you send requests to your firewall
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external IP address does not mean that the request will be associated
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with the external interface or the <quote>net</quote> zone. Any
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traffic that you generate from the local network will be associated
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with your local interface and will be treated as loc->fw
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traffic.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">IP addresses are properties of systems,
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not of interfaces</emphasis>. It is a mistake to believe that your
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firewall is able to forward packets just because you can ping the IP
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address of all of the firewall's interfaces from the local network.
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The only conclusion you can draw from such pinging success is that the
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link between the local system and the firewall works and that you
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probably have the local system's default gateway set correctly.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">All IP addresses configured on firewall
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interfaces are in the $FW (fw) zone</emphasis>. If 192.168.1.254 is
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the IP address of your internal interface then you can write
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<quote><emphasis role="bold">$FW:192.168.1.254</emphasis></quote> in a
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rule but you may not write <quote><emphasis
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role="bold">loc:192.168.1.254</emphasis></quote>. Similarly, it is
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nonsensical to add 192.168.1.254 to the <emphasis
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role="bold">loc</emphasis> zone using an entry in
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<filename>/etc/shorewall/hosts</filename>.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">Reply packets do NOT automatically follow
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the reverse path of the one taken by the original request</emphasis>.
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All packets are routed according to the routing table of the host at
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each step of the way. This issue commonly comes up when people install
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a Shorewall firewall parallel to an existing gateway and try to use
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DNAT through Shorewall without changing the default gateway of the
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system receiving the forwarded requests. Requests come in through the
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Shorewall firewall where the destination IP address gets rewritten but
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replies go out unmodified through the old gateway.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">Shorewall itself has no notion of inside
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or outside</emphasis>. These concepts are embodied in how Shorewall is
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configured.</para>
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</listitem>
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</itemizedlist>
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</section>
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<section>
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<title>Your Network Environment</title>
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@ -187,7 +100,7 @@ iptables: No chain/target/match by that name
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<itemizedlist>
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<listitem>
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<para>Port Forwarding where client and server are in the same subnet.
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See FAQ 2.</para>
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See <ulink url="FAQ.htm#faq2">FAQ 2</ulink>.</para>
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</listitem>
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<listitem>
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@ -228,11 +141,35 @@ iptables: No chain/target/match by that name
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<section>
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<title>Connection Problems</title>
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<para>If the appropriate policy for the connection that you are trying to
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make is ACCEPT, please DO NOT ADD ADDITIONAL ACCEPT RULES TRYING TO MAKE
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IT WORK. Such additional rules will NEVER make it work, they add clutter
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to your rule set and they represent a big security hole in the event that
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you forget to remove them later.</para>
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<para>One very important thing to remember is that not all connection
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problems are Shorewall configuration problems. If the connection that is
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giving you problems is to or from the firewall system or if it doesn't
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rely on NAT or Proxy ARP then you can often eliminate Shorewall using a
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simple test:</para>
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<itemizedlist>
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<listitem>
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<para><command>/sbin/shorewall clear</command></para>
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</listitem>
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<listitem>
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<para>Try the connection. If it works then the problem is in your
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Shorewall configuration; if the connection still doesn't work then the
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problem is not with Shorewall or the way that it is configured.</para>
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</listitem>
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<listitem>
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<para>Be sure to <command>/sbin/shorewall start</command> after the
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test.</para>
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</listitem>
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</itemizedlist>
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<para>If you still suspect Shorewall and the appropriate policy for the
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connection that you are trying to make is ACCEPT, please DO NOT ADD
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ADDITIONAL ACCEPT RULES TRYING TO MAKE IT WORK. Such additional rules will
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NEVER make it work, they add clutter to your rule set and they represent a
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big security hole in the event that you forget to remove them
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later.</para>
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<para>I also recommend against setting all of your policies to ACCEPT in
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an effort to make something work. That robs you of one of your best
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@ -354,6 +291,62 @@ Ping/DROP net all</programlisting>
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</itemizedlist>
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</section>
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<section>
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<title>Some Things to Keep in Mind</title>
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<itemizedlist>
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<listitem>
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<para><emphasis role="bold">You cannot test your firewall from the
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inside</emphasis>. Just because you send requests to your firewall
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external IP address does not mean that the request will be associated
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with the external interface or the <quote>net</quote> zone. Any
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traffic that you generate from the local network will be associated
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with your local interface and will be treated as loc->fw
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traffic.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">IP addresses are properties of systems,
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not of interfaces</emphasis>. It is a mistake to believe that your
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firewall is able to forward packets just because you can ping the IP
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address of all of the firewall's interfaces from the local network.
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The only conclusion you can draw from such pinging success is that the
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link between the local system and the firewall works and that you
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probably have the local system's default gateway set correctly.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">All IP addresses configured on firewall
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interfaces are in the $FW (fw) zone</emphasis>. If 192.168.1.254 is
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the IP address of your internal interface then you can write
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<quote><emphasis role="bold">$FW:192.168.1.254</emphasis></quote> in a
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rule but you may not write <quote><emphasis
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role="bold">loc:192.168.1.254</emphasis></quote>. Similarly, it is
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nonsensical to add 192.168.1.254 to the <emphasis
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role="bold">loc</emphasis> zone using an entry in
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<filename>/etc/shorewall/hosts</filename>.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">Reply packets do NOT automatically follow
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the reverse path of the one taken by the original request</emphasis>.
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All packets are routed according to the routing table of the host at
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each step of the way. This issue commonly comes up when people install
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a Shorewall firewall parallel to an existing gateway and try to use
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DNAT through Shorewall without changing the default gateway of the
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system receiving the forwarded requests. Requests come in through the
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Shorewall firewall where the destination IP address gets rewritten but
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replies go out unmodified through the old gateway.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">Shorewall itself has no notion of inside
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or outside</emphasis>. These concepts are embodied in how Shorewall is
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configured.</para>
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</listitem>
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</itemizedlist>
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</section>
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<section>
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<title>Other Gotchas</title>
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@ -379,6 +372,11 @@ Ping/DROP net all</programlisting>
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interface in <ulink
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url="Documentation.htm#Interfaces"><filename>/etc/shorewall/interfaces</filename></ulink>.</para>
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</listitem>
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<listitem>
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<para>You have connected two firewall interfaces (from different
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zones) to the same hub or switch.</para>
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</listitem>
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</orderedlist>
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</listitem>
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@ -396,14 +394,8 @@ Ping/DROP net all</programlisting>
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directions</emphasis>. So when setting up routing between <emphasis
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role="bold">A</emphasis> and <emphasis role="bold">B</emphasis>, be
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sure to verify that the route from <emphasis role="bold">B</emphasis>
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back to <emphasis role="bold">A</emphasis> is defined.</para>
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</listitem>
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<listitem>
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<para>Some versions of LRP (EigerStein2Beta for example) have a shell
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with broken variable expansion. You can get a corrected shell from the
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<ulink url="ftp://ftp.shorewall.net/pub/shorewall/ash.gz">Shorewall
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Errata download site</ulink>.</para>
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back to <emphasis role="bold">A</emphasis> is defined and
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correct.</para>
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</listitem>
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<listitem>
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@ -437,84 +429,4 @@ Ping/DROP net all</programlisting>
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<para>See the <ulink url="support.htm">Shorewall Support
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Page</ulink>.</para>
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</section>
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<appendix>
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<title>Revision History</title>
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<para><revhistory>
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<revision>
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<revnumber>2.0</revnumber>
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<date>2005-09-11</date>
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<authorinitials>CR</authorinitials>
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<revremark>Updated for Shorewall 3.0</revremark>
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</revision>
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<revision>
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<revnumber>1.9</revnumber>
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<date>2004-08-25</date>
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<authorinitials>TE</authorinitials>
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<revremark>Advice for the networking-challenged.</revremark>
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</revision>
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<revision>
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<revnumber>1.8</revnumber>
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<date>2004-04-03</date>
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<authorinitials>TE</authorinitials>
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<revremark>Point out that firewall addresses are in the $FW
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zone.</revremark>
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</revision>
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<revision>
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<revnumber>1.7</revnumber>
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<date>2004-02-02</date>
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<authorinitials>TE</authorinitials>
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<revremark>Add hint about testing from inside the
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firewall.</revremark>
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</revision>
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<revision>
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<revnumber>1.6</revnumber>
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<date>2004-01-06</date>
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<authorinitials>TE</authorinitials>
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<revremark>Add pointer to Site and Mailing List Archives
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Searches.</revremark>
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</revision>
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<revision>
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<revnumber>1.5</revnumber>
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<date>2004-01-01</date>
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<authorinitials>TE</authorinitials>
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<revremark>Added information about eliminating ping-generated log
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messages.</revremark>
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</revision>
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<revision>
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<revnumber>1.4</revnumber>
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<date>2003-12-22</date>
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<authorinitials>TE</authorinitials>
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<revremark>Initial Docbook Conversion</revremark>
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</revision>
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</revhistory></para>
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</appendix>
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</article>
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