Turris Omnia–an open-source, open-hardware router by the Czech Internet registry

Should be pretty quick! we build appliances with the Armada 370 CPUs (Single core Cortex A8, but same Ethernet and bus IP), and they can route/NAT at 800-1000 megabits between 2 interfaces (at 1500 byte packets)

PC has been a "router" for a long time.