In 2004 an acquaintance asked me for help with sharing an Internet connection to the residents of his condominium after he had failed getting a common router/switch solution to work. The router was not playing ball unless all clients presented themselves in one and the same subnet, which prompted the unmanaged switch to pass traffic directly between the ports, and that was a no-no for historic reasons relating to Windows and its malware of the time. So I repurposed an old anno 1999 ATX motherboard with a mix of Ethernet cards - the board offered 6 PCI ports and the condominium has 5 residents - 256 MB of RAM, and a low-power passively cooled Pentium III to act as router and switch in one, running OpenBSD with some dhcpd(8) and pf(4) to manage clients and traffic.
16 years later this set-up is still in use 24/7 due to ISPs claiming logistic problems preventing them from installing gateway equipment in the building. It serves a VDSL2 line of 60/20 Mbit/s coming in over the POTS. At its peak the computer had 6 years of uptime. It is still running OpenBSD 3.5 due to poor #OPSEC on my behalf.