How to make a VPN server from a PC (windows, linux)?

Question

openvpn

Friends!
We have three subnets: office and two shops. In the office, there is Asus N10 with dd-wrt as a server, in stores there are the same devices as clients. In addition, there are several more clients connecting via VPN from Windows. If the number of clients >= 3, then incomprehensible glitches begin with network printers in the office - they stop printing until the router, which is the VPN server, is rebooted. (Perhaps someone knows why and how to solve this issue. My guess is that the device can not cope with the traffic? But this is not the main question). I want to replace the router with, for example, an old computer on Windows or Linux. Question - which OS is better to choose and where to find setup manuals? Offhand did not google.
Main subnet (office) 192.168.10.0
Store1 192.168.20.0
Store2 192.168.30.0
Thank you!

Answer 1

You should learn how to google first... Here are almost the first links on your request:
www.sergeysl.ru/freebsd-openvpn-x509
vds-admin.ru/unix-linux/nastroika-openvpn-servera-...
wiki.dieg .info/openvpn
and the most comprehensive material
habrahabr.ru/post/233971
And the OS in the Unix world is chosen to their liking...