Serial Crossover

2026-10-20 Serial Crossover Today, OpenBSD 8.0 was released so it's time to think about upgrading my servers. A few days ago I noticed that my firewall had reached nearly a year of uptime which made me realise that I must have missed upgrading to OpenBSD 7.9. So it's overdue for a refresh. My firewall is a headless machine running on a Unifi Security Gateway 4. It has a console port which I connect to using a rollover cable, which for some reason requires the use of a crossover adapter when I connect it to my DB9 to USB cable. My problem was that I'd lost mine. I pulled out my half-baked notes from a few years ago and learnt again what I need to make. I use two DB9 connectors separated with standoffs and linked together thusly: Fig.1 - Crossover Wiring Schematic This'll re-route the TX to the RX so that the machines hear what each other are saying. © 2026 altos.au. This work is licensed under CC BY-NC-ND 4.0.