c'mon boy....you have to create LAN client first...the linux machine which u want to ssh will be the LAN client...ok....so in LAN client setting where it asks for the LAN IP address...give it the address of ur linux machine and then do the port forwarding for port 22 to that LAN client...and u see u dont have to type the IP in portmap section...just type 22 there..FOR EXAMPLE
start port= 22
end port= 22
port map =22
or simply call PTCL support guys...they will help u in port forwarding...not an issue...