In many institutions, a lot of sites are blocked and we naturally try to circumvent the blocks using VPNs or proxies. If you use a VPN like OpenVPN, the client can be configured to send DNS requests through the VPN.
When you use SSh however, you will have to manually add a entry to firefox proxy control. However by default, firefox does not route the DNS requests through the SSH tunnel, instead it decides to use the default network. This can be annoying as the sites will not load and you might also get in trouble with the Network Administrator.Fortunately you can tunnel requests using a simple switch.
Open a new tab and type about:config. You should see something like this.