Most Common Context: APC / Network UPS Configuration

In UPS network management cards (like APC’s NMC), NAT mode relates to how the UPS communicates through a network where NAT is in use (e.g., behind a router). Issues can arise because:

• The UPS management card may broadcast on the local subnet and not traverse NAT properly
• SNMP traps or NUT (Network UPS Tools) communications can be blocked

NUT (Network UPS Tools) — Client/Server Mode

In NUT, there are connection modes:

• netserver — the UPS is connected locally and shared over the network
• netclient (NAT consideration) — clients connect to the server by IP; if NAT is involved, you need to ensure the correct IP is reachable and port 3493 is forwarded

Virtualization Context (VMware / Proxmox / Hyper-V)

If you’re running a UPS monitor in a VM, NAT mode refers to the VM’s network adapter mode:

• NAT mode = the VM shares the host’s IP; the UPS daemon on the VM may not be reachable from other machines
• Fix: Switch the VM’s network adapter to Bridged mode so it gets its own IP on the network, making the UPS server accessible to other devices

This is a very common issue when running NUT or APC PowerChute in a VM.