Dante Clock Sync: Fixing Multiple Leader Clocks
Dante Clock Sync: Fixing Multiple Leader Clocks
Dante uses Precision Time Protocol (PTP v1, IEEE 1588-2002) to keep every device on the network sample-accurate. Each network typically elects one Primary Leader Clock — the master reference that all other devices lock to. When Dante Controller's Clock Status tab shows more than one Primary Leader, something is preventing PTP traffic from propagating correctly and your network is at risk of dropouts.
Symptoms of a Multiple-Leader Problem
The following combination of symptoms indicates a clock synchronisation issue rather than an audio routing problem:
- More than one device listed as Primary Leader Clock in Dante Controller
- Devices missing from or partially visible in Dante Controller
- Unusually high network bandwidth across all devices (multicast flooding)
- Windows PCs running Dante Virtual Soundcard listed as "Listening" rather than "Leader" or "Follower"
If Dante Controller shows multiple leaders but audio is stable and no other symptoms are present, the network may be functioning correctly. Address it only if you are experiencing problems.
Root Cause: IGMP Snooping
The most common cause is incorrectly configured — or absent — IGMP snooping on managed switches. PTP uses multicast addressing. Without IGMP snooping, PTP packets flood every port on the switch. Each device receives PTP announcements from every other device directly, and multiple Best Master Clock Algorithm (BMCA) elections run in isolation, producing multiple winners.
When to Disable IGMP Snooping
On small, isolated networks — a single switch, all Dante devices, no other multicast sources — disable IGMP snooping and multicast filtering entirely. The volume of Dante multicast at this scale (clocking, discovery, control only — audio uses unicast by default) is low enough that flooding is harmless.
Alternatively, use an unmanaged Gigabit switch that does not support Energy Efficient Ethernet. Unmanaged switches with no EEE work reliably for small systems.
When to Configure IGMP Snooping
Enable IGMP snooping on managed switches when:
- Multicast Dante or AES67 audio flows are in use
- The network carries other multicast traffic (IP video, Crestron, AMX)
- 100 Mbps devices are present
- A Wi-Fi access point is on the same network segment
IGMP snooping constrains multicast delivery — audio and PTP packets only reach ports that have joined the relevant multicast groups. This prevents saturation of the switch backplane and solves the multiple-leader problem by ensuring PTP traffic flows correctly to all devices.
IGMP Configuration Rules
When enabling IGMP snooping:
- Query interval: set to 30 seconds
- Filter Unregistered Multicast: must be OFF. This feature is enabled by default on some switches and will block mDNS (device discovery), PTP, and Dante control traffic — devices disappear from Dante Controller
- Fast Leave: harmless on a Dante network; may be required for multicast video on the same switch
- IGMP querier: only one per network/VLAN. Do not configure multiple queriers
- IGMP proxy / PIM routing: not supported
If devices are still missing after configuring IGMP snooping, you may need static IGMP routes. Add static membership entries for:
- PTP traffic:
224.0.1.129to224.0.1.132 - Dante control:
224.0.0.230,224.0.0.231,224.0.0.232,224.0.0.233 - Any specific Dante or AES67 multicast audio group addresses in use
Only add static routes if the switch still misbehaves after standard IGMP configuration.
Reading Bandwidth in Dante Controller
Dante Controller's network status view shows per-device receive bandwidth. If any device shows Rx Bandwidth in yellow or red, multicast traffic is high enough that IGMP snooping is needed — even if audio is currently stable. A yellow or red reading is a leading indicator of future instability.
For the full list of Dante ports and multicast addresses, refer to Audinate's port reference: https://www.audinate.com/learn/faqs/which-network-ports-does-dante-use
Further Training
For in-depth network configuration knowledge — including VLAN design, switch hardening, and advanced IGMP scenarios — the Dante Level 3 Certification course covers this material in detail.
This article was adapted from Audinate's original guidance: "Multiple Leader Clocks" — https://support.getdante.com/hc/en-gb/articles/5285123768607-Multiple-Leader-Clocks Habitech-edited for UK trade installer context. Original © Audinate Pty Ltd.