Art-Net troubleshooting checklist: subnet, firewall, node and universe mistakes

Work the list in order

Do not start by rebuilding the show. Confirm the output interface IP is on the same subnet as the node. Confirm the OS firewall allows UDP 6454. Confirm the universe number matches the node. Confirm the fixture start address matches the patch. Then suspect the cable.

A visualiser receiving Art-Net is a useful test. It does not prove the hardware node is in the same universe or on the same NIC.

Layer 1 and 2: cable, link, IP

Link light on the node. Link light on the dock. Wrong dongle selected in software. VPN capturing the default route. A second Ethernet adapter with a similar 2.x address you forgot existed.

Ping the node. No ping means you do not have a lighting problem yet — you have a network problem. Fix the subnet mask and IP before you touch the patch. 2.0.0.10/8 and 10.0.0.10/24 are not a conversation. They are two rooms.

Layer 3: firewall and the right NIC

Windows Defender, macOS application firewall, corporate endpoint software: any of them can drop UDP 6454. Disable the firewall for a ten-second test on a dedicated show NIC if policy allows, then add a permanent allow rule. Do not leave the firewall off.

Bind the sender to the show NIC explicitly. “Any interface” plus a Wi-Fi card is how packets leave through the air and die.

Universe, net and the node front panel

Read the node’s display, not last year’s spreadsheet. Universe 0 versus 1 is the usual off-by-one. Some nodes number ports 1–4 independently of Art-Net universe; others map port 1 to universe 0. Change one variable at a time and send a full-on on channel 1.

Broadcast versus unicast: if unicast is aimed at an old IP, the node hears nothing while Wireshark on the PC still shows outgoing packets. Update the destination list when you change a node IP.

DMX after the node

If the node’s DMX LED is cooking and the fixture is dark, you have left Ethernet. Check XLR, terminator, start address, personality, and whether the fixture is in a mode that expects more channels than you are sending.

Swap in a known-good cable and a known-good fixture at address 1. If that works, the software and the node are innocent. Walk the chain.

A five-line report for the next person

Write: PC IP and NIC name, node IP, Art-Net universe, node port, first fixture address. The next technician should not have to reverse-engineer your laptop at 18:00.

Tools that help without lying

A packet capture proves the PC sent something. It does not prove the node listened. A node DMX LED proves the node is outputting something. It does not prove channel 17 is the dimmer you think it is. Use both, in that order.

A known-good USB DMX dongle on one fixture isolates Ethernet. If USB DMX works and Art-Net does not, stop editing fixture addresses. If both fail, the fixture or the XLR is the story.

When you are tired, change one thing and write it down. Three simultaneous “fixes” create a fourth problem you will blame on Art-Net.

When it is actually the fixture

A fixture in the wrong personality will look like a universe error. Confirm the mode on the display. A fixture that lost its address after a power dip will look like a node error. Re-address from the menu, then update the paper patch.

Heat and cheap PSUs make intermittent DMX. If a head dies after an hour and the node LED is still happy, feel the PSU. Lighting problems are allowed to be electrical.

Keep one cheap PAR as a known-good tester. It has saved more load-ins than a second visualiser licence.

Call it when it is environmental

A switch that reboots when the smoke machine trips a circuit is not Art-Net. A node on the same power as a subwoofer amplifier will brown out and look like packet loss. Isolate power the same way you isolate data.

If the problem follows a person with a wireless talkback pack, you may have RF near a cheap node. Move the pack. Superstition that “Art-Net hates this room” is usually a cable, a PSU, or a subnet.

Related

• What is Art-Net? →
• DMX over Ethernet →
• Patching →