How to Bypass Proxy Servers for Internal Addresses in Firefoxby Mike Venture
Connecting to the Internet through proxy servers has some advantages, like anonymity and the ability to block websites. When accessing computers on your local network, however, those advantages don't apply -- yet the disadvantages, such as reduced speed and increased latency, remain. The best thing to do is to configure Firefox to connect directly to computers on your local network, bypassing the proxy altogether.
Launch Firefox. Click the "Firefox" button and click "Options."
Select the "Advanced" panel, then the "Network" tab.
Click the "Settings" button to open the Connection Settings dialog. Manual Proxy Configuration should already be selected; if not, select it and enter your proxy settings.
Enter the local IP addresses or hostnames for which you want Firefox to bypass the proxy server. If you want to bypass the proxy server for all local IP addresses, enter "10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, <local>" without quotation marks.
Close the Connection Settings and Options dialogs. Restart Firefox.