Build a
normal tunnel between Server #1 and #2 .. --
dev tun
the rest of your machines do not need to be included in the VPN.
If you want [
to go insane]
build a bridge between your Servers #1 and #2 .. --
dev tap (bridge at both ends)
the rest of your machines do not need to be included in the VPN.
YMMV -- Good luck and let me know if it works 8-)