UDM Pro Max: port forwards break after moving WAN to the SFP+ port
September 14, 2026
Problem
Port forwards stopped working after moving the ISP handoff from the RJ45 WAN port to the SFP+ WAN port on a UDM Pro Max. Traffic that used to reach internal hosts no longer arrived.
Cause
Moving the handoff changed which interface was acting as the active WAN. The port-forward and WAN-interface settings still referenced the old WAN (WAN1 vs WAN2), so rules were being applied to the wrong uplink.
Fix
- Confirm which WAN the SFP+ port maps to (WAN1 or WAN2) in the UniFi network settings.
- Update the port-forwarding rules so they apply on the WAN interface that now carries the ISP connection.
- Check the WAN priority / failover order so the SFP+ interface is the primary.
- Re-test each forward from outside the network, not from inside — internal tests can succeed via hairpin even when the external path is broken.