2026-09-27

If you're self-hosting anything that matters — Nextcloud, Home Assistant, cameras, a VPN back into your network — a single internet connection is a single point of failure. Jeff Geerling's latest post walks through adding a backup WAN gateway on OPNsense, and it's a genuinely useful reference for homelabbers running firewalls on mini PCs or repurposed hardware.

The setup covers configuring a secondary ISP connection (or a 4G/5G dongle) as a failover gateway in OPNsense, so if your primary line drops, traffic automatically routes over the backup. Jeff goes through interface assignment, gateway priorities, and the monitoring settings that trigger the switchover. It's the kind of thing that sounds complicated but OPNsense handles reasonably well once you know where the settings live.

Why homelabbers should care

Redundant WAN isn't just for businesses. If you're exposing services via Cloudflare Tunnel or reverse proxy, or relying on remote access while you're away from home, a dropped connection means everything goes dark. A cheap 4G SIM in a USB dongle can keep critical services ticking over for pennies.

Caveats

Failover isn't load balancing — you won't get combined speeds. The switchover isn't instant either; there's a detection delay depending on your monitoring interval. And if your backup is a mobile connection, watch out for CGNAT, which will block inbound connections unless you're tunnelling out. Jeff covers some of these gotchas but it's worth testing your specific setup.

What you need

If you're running OPNsense on a mini PC, you likely already have (or can add) a second NIC or USB Ethernet adapter. A basic 4G USB dongle with a data SIM is the cheapest backup path. For connecting any USB peripherals or storage to your firewall box, a decent cable helps — 240W USB-C Fast-Charging & Data Cable – Braided, LED Indicator is solid for USB-C gear. For the router hardware itself, OPNsense mini PC options on Amazon start well under £200.