Raw TCP/IP port forwarding software

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http://serverfault.com – I have server which IP address is whitelisted in some external system. And also, I have a few software developers with dynamic IPs which develop software and they need to connect to external system, but their IPs are not whitelisted, and cannot be whitelisted, because they are dynamic ones. So, I have server with IP which connects to external system and that system knows (by firewall rule, etc) that is in white list and allow connection. But developers have dynamic IP (a few class B networks, no way to whitelist so many addresses). Is there any software, TCP/IP port forwardin ()