Just use linux! Why use someone else's non FOSS, locked down linux, when you could truly own your router? It's a great educational experience I would recommend to anyone interested in networking. Grab debian, grab a system with 2 NICs, make it your router/firewall/gateway.
> Grab debian, grab a system with 2 NICs, make it your router/firewall/gateway. The problem with this (assuming you meant a generic (x86?) system) is that you won't get wire speed processing (no hardware offloading), so network performance will suffer. Unless you buy a dedicated router board (which is typically ARM), like say something like the Banana Pi BPI-R4. But installing/configuring a standard distro line Debia…
Setting up Debian as a router might take some effort but it's certainly not difficult. Enabling routing is a single line config change, install dhcpd and you're almost there. I'd certainly recommend the router OS.