Guide
sACN Troubleshooting: Multicast vs Unicast, IGMP & Why Switches Break Shows
A practical guide to sACN (E1.31): multicast vs unicast, IGMP, switch behavior, and how to stop lighting glitches on networks.
Kristoffer NerskogenJanuary 12, 2026What sACN Is Designed For
sACN (ANSI E1.31) is:
DMX over Ethernet
UDP-based
Designed for large, distributed systems
Unlike Art-Net, sACN assumes:
Managed switches
Multicast awareness
Network discipline
That’s both a strength and a trap.
Multicast vs Unicast (This Matters More Than You Think)
Multicast (Default)
Universes mapped to multicast groups
Efficient at scale
Requires correct IGMP handling
Unicast
Data sent directly to receivers
Easier to debug
Higher sender load
Rule of thumb
Small systems → Unicast
Large systems → Multicast (done properly)
IGMP: The Silent Show Killer
IGMP controls who receives multicast traffic.
If IGMP is:
Disabled → multicast floods everything
Misconfigured → receivers get nothing
Over-optimized → packets are dropped
Common symptoms:
Lights flicker only when more universes are active
Works for minutes, then freezes
One fixture works, another doesn’t
Why “Better” Switches Often Break sACN
Managed switches introduce:
IGMP snooping
QoS
Storm control
Energy-saving features
These are great for offices — terrible for lighting if misconfigured.
Safer switch behavior
IGMP snooping enabled
Querier present
Storm control off
QoS disabled or neutral
If timing feels inconsistent, read: DMX Timing & Refresh Rate
Universe Planning Still Matters
Even with Ethernet, DMX rules still apply.
Bad planning causes:
Unnecessary multicast load
Hard-to-debug conflicts
Perceived latency issues
Good planning is covered in: DMX Patch Lists & Channel Planning
sACN Troubleshooting Checklist
Start with unicast
Verify receiver IPs
Confirm universe → multicast mapping
Check IGMP querier presence
Test on an unmanaged switch
Scale up slowly
If it works on an unmanaged switch but not a managed one — the switch is the problem.
sACN vs Art-Net (Reality Check)
Feature | Art-Net | sACN |
|---|---|---|
Setup simplicity | Easy | Moderate |
Scalability | Limited | Excellent |
Network discipline | Low | High |
Failure mode | Loud | Silent |
A deeper comparison lives here: Art-Net vs sACN vs ALPINE
Why Modern Systems Move Beyond Both
Art-Net and sACN both:
Trust the network
Assume correct configuration
Lack identity and ownership
Modern control stacks need:
Device identity
Capability negotiation
Deterministic behavior
That’s the motivation behind: ALPINE, identity first lighting protocol
Summary
sACN is powerful — but unforgiving.
If:
Multicast isn’t understood
Switches aren’t lighting-aware
Planning is sloppy
Then sACN will fail silently.
When configured correctly, it scales far beyond Art-Net — but it demands respect.