You may use the FoxyProxy Standard for Firefox and Chrome to proxy only matched URL patterns. This removes the hassle of having to regularly enable/disable a proxy.
The Chrome version is more fiddly to setup, as you must set a shortcut to include the --host-resolver-rules flag due to the way the browser handles DNS. On Windows, the Start Menu shortcut for Chrome is located in the following location:
%programdata%\Microsoft\Windows\Start Menu\Programs
Update the Target (note that this is 32-bit Chrome) from:
"C:\Program Files (x86)\Google\Chrome\Application\chrome.exe"
to:
"C:\Program Files (x86)\Google\Chrome\Application\chrome.exe" --host-resolver-rules
Unpin and repin and start menu and taskbar shortcuts to Chrome afterwards.
Proxy:
Title: Vagrant
Proxy Type: SOCKS5
Proxy DNS?: On (Firefox only)
IP Address: 127.0.0.1
Port: 2080
White Patterns:
Name: Vagrant
Pattern: *.vagrant.localdomain*
Type: wildcard
http(s): both
On/Off: on