Configuring firefox to use a chain proxy

I live in college and I access internet through a local http proxy. I want to access internet through external http/SOCKS5 proxies which are freely available. How to configure Firefox to do that?

Scenario:

My_comp <-->local http_proxy <--> external http_proxy <--> internet

Solution 1:

One way to access an External Proxy behind an Internal proxy is to SSH External Proxy (if remote SSH enabled) and bind the connection to a specific port in your system. Thereafter, use the port and 127.0.0.1 as Network Options (Socks5) for Firefox.

If the system you've is Linux, type in Terminal ssh -D Port_no user@server_address server_port, where,

• Port_no is the binding port you can select for the system, try a port greater than 1024;
• user is the username provided by external proxy;
• server_address is the IP address of the external proxy;
• server_port is the port where the Server is receiving the SSH connection;

For Windows,many prefer Putty, but I would not be able to assure how it will work.

About Putty : PuTTY is an SSH and telnet client, developed originally by Simon Tatham for the Windows platform.

Link for Putty : Here.