Hmm I’ve got an old Compaq 575e with a PCNet32 nic, and an old 3com 3c509 ISA adapter in a closet with 10base2 and AUI ports.

Use a modem router or managed switch to get down to 100baseT, give this box a Linux distro, enable Ethernet bridging in the kernel, and slaps case this baby can drop almost 20k packets a second, no sweat!