We have 2 offices connected with a fiber optics cables. On both sides FO is inserted into the fiber ports in the switches but we can install fiber pci-e cards in some servers if required.
The offices are small, all people generally trust each other, the LAN is insecure inside and we would rather leave it this way than building a strong security.
The fiber cable goes about 500m thru a public areas, it's easily accessible and could be used by someone to get access inside our LAN.
The idea is to build an encrypted channel between 2 offices to avoid any intrusion thru that cable.
What devices/software can you recommend? We need to have fully working ~1000mbit/sec link with the minimal system load. For example, if the offices will be connected with OpenVPN or similar software, will it be able to handle a gigabit connection? What server load should we expect? All servers are equipped with a similar CPUs - Core Quad 9440 but of course I don't want to use the whole CPU for VPN.
Having some separate device would be better, especially if the bridge will be transparent to TCP/IP.
The offices have no dedicated server rooms so we would like to avoid installing any loud industrial switches/routers.