A Gnome Shell extension for switching between manual and automatic proxy settings.
All you need to preset your manual and automatic proxy settings from the network manager, and, install the gnome shell extension “Proxy Switcher” from Gnome Shell extensions website.
Before installation make sure the Gnome Shell integration is working fine with your web browser. Then, you will find a switch button to install/uninstall the extension.
Also, you can install and install extension using “Gnome-Tweak-Tool”
For Ubuntu users “Including the development release Ubuntu 14.04 LTS Trusty Tahr”.
sudo apt-get install gnome-tweak-tool
For Fedora Users “Fedora 20″
yum install gnome-tweak-tool
After installing the Proxy Switcher extension, its files will be available in this directory.