<p>If you are still having problems, open the Message Log (in the Window menu) and post the debug output on the <ahref="http://transmission.m0k.org/forum/viewforum.php?f=2">support forums</a>.
<ol>
<li>Pause your torrents</li>
<li>Clear the log and set it to 'Debug'</li>
<li>Toggle "Automatically forward port" in Network Preferences</li>
<li>UPnP is enabled. Consult your router's documentation for instructions. If your router doesn't support UPnP, you will have to forward <ahref="pfrouter.html">manually</a>.</li>
<li>DMZ mode is disabled.</li>
<li>The port has not already been forwarded manually.
<p>For example, your network might resemble the following: <b>ADSL modem/router --> Airport extreme --> MacBook.</b>
<p>If you have multiple routers in your home network (such as in the example above), you have two options. The easiest way is to turn one of the routers into 'Bridge mode' which means you then only have to configure one device rather than all of them. So, in our above example, we would set the Airport extreme to 'Bridge'. See your router's help documentation for instructions.
<p>The second way is to map Transmission's port on all of the devices on your network.
Transmission can only automatically port map the router the computer is directly connected to. Any others in between this router and your modem will have to be <ahref="pfrouter.html">forwarded manually</a>. For detailed instructions, <ahref="http://www.portforward.com/help/doublerouterportforwarding.htm">click here</a>.
<p>Finally make sure the OS X firewall is either disabled, or you have <ahref="pffirewall.html">allowed Transmission's port</a>.
The firewall can cause the port to remain closed, even if it has been successfully mapped by the router(s).