I need to deploy ~75 routerboards as remote VPN clients, so users have ethernet handoffs with their VPN, mainly for VOIP applications. Has anyone else done this, or have any suggestions as how best to accomplish it? The issue's I see are that users will have dynamic internet addresses, these routers will be behind god knows what kind of firewalls. My first thought was to try openVPN, but I hear that support will/has been dropped for it?

Any ideas are appreciated, thanks!

http://wiki.mikrotik.com/wiki/Manual:TOC

Read the section on VPNs. There are several choices. Yes OpenVPN development has been halted, and if I remember correctly it only ever worked with TCP, so the tunnel could not be built using UDP. What you choose really depends on what you want to do, most of the PPP protocols should allow you to have the router dial in from any IP address/location to a set IP address. For that many tunnels you will obviously want a more powerful router as the server than what you have at remote locations. So then for that it comes down to desired throughput, how secure you want the tunnel to be, and processing power.

It absolutely works and it works great. We use this for our business and haven't had any problems.

Are you referring to open VPN?