SSH tunnel to computer behind dd-wrt router
I'm currently trying ssh tunnel to a Linux box behind my home dd-wrt router. I'm using PuTTY as the client as I will mainly be connecting to it from windows machines. I have been able to connect to it successfully from another computer on my home network but there are issues when I attempt it from off site. I have also enabled ssh on the router itself for management and tunneling. The location I'm tunneling from has a proxy and firewall with ports 22 and 443 open.
Here's the issue. When I use the router's external IP address, port 443, and the appropriate proxy settings, I am able to connect to the router itself via ssh. If I use port 22, which I think I have forwarded to the box, I get this error message: "Error Code: 502 Proxy Error. The specified Secure Sockets Layer (SSL) port is not allowed. ISA Server is not configured to allow SSL requests from this port. Most Web browsers use port 443 for SSL requests."
I'm new to networking in general and would greatly appreciate any assistance.
Thanks in advance!