How to set up a vpn connection on a computer connected via a router?

Question

VPN

How to set up a vpn connection on a computer connected via a router?
It works directly, it does not connect through the router with error 619. The DIR-300 router, firmware version 1.0.4, did not find the VPN Pass Through settings. It is not possible to work directly, other computers are connected to the router, a second network card is impossible, the computer is under warranty, there is no time to carry.

Answer 1

There is an option to put an alternative firmware on the router.

Answer 2

VPN connection where? Maybe "there" support other communication protocols? For example, "armor-piercing" OpenVPN or "invisible" SSTP, or maybe Hamachi will be launched "there"?