Does IGMP affect Dante Devices?
Dante enabled devices can exhibit communications issues with switches that use IGMP (Internet Group Protocol Management) Snooping if the switch is not configured correctly. Many switches have this feature disabled by default (Juniper switches usually have IGMP snooping enabled.) Turning off IGMP snooping will usually solve this problem. For small, isolated networks that only have Shure devices, or when there is an isolated VLAN for Shure gear, you should DISABLE IGMP Snooping.
Dante flows are, by default, unicast (a one-to-one connection between two devices, versus transmitting packets to multiple destinations - multicast). For networks that only use unicast flows, disabling IGMP snooping shouldn't cause any problems. However, before making changes to your network or switch settings, consult with an IT professional.
A good way to diagnose this problem is by using Dante Controller software (available as a free download from www.audinate.com). Dante Controller allows you to see which device is acting as the Master Clock on the network. There should only be one clock master. If Controller is reporting multiple clock masters, IGMP snooping is likely the culprit.
There are cases where IGMP snooping is beneficial. IGMP helps prevent transmission of multicast data packets to ports that don't need them. On larger, shared networks with lots of Dante multicast flows, IGMP snooping greatly reduces the amount of multicast traffic on the network by only forwarding multicast data to the devices that request it.
In these cases, a knowledgeable IT professional should be engaged to ensure proper configuration. In order to support Shure products with Dante on a network, multicast operation should be allowed. Please do not make changes to an enterprise network without proper authorization.
How to configure IGMP Snooping
Most switches today are able to function as an IGMP querier. The querier periodically sends query messages to all hosts on multicast address 184.108.40.206 asking ""What group addresses do you want?"" The host(s) respond with a membership report to 220.127.116.11 (or 18.104.22.168) with ""I want A.B.C.D.""
Ensure that there is only ONE active querier per VLAN. Multiple queriers can technically be configured amongst some manufacturers' equipment. However for Dante enabled networks you should only have ONE active querier per VLAN. As of 2017, IGMPv3 is the latest version, which is ideal for use with Dante, although v2 can be used.
Set the querier interval short (15 or 30 seconds). This minimizes the potential for gaps in audio and increases responsiveness. Leave the timeout values at default settings. Longer timeout settings are better in most cases.
Add IGMP static filters to each port on the VLAN. This ensures the PTP, mDNS, and Discovery traffic is always available throughout the VLAN. IGMP static filters would be required for:
- PTP traffic: 22.214.171.124
- mDNS traffic: 126.96.36.199
- Shure discovery: 188.8.131.52
Ideally these IGMP settings will be configured on a core network switch, or the router port.
Example IGMP Snooping setup using Cisco SG300
- Open the Multicast menu.
- Enable Bridge Multicast Filtering.
- For each VLAN, select ""IP Group Address"" as the Forwarding Method.
Open the IGMP Snooping menu and enable Snooping.
- Edit each VLAN setting.
- Enable Snooping Status & Querier Status.
- Set Query Interval to minimum value: 30 seconds.
Select IGMPV3 as the Querier version.
- If you experience intermittent audio, then run a Wireshark trace. It may show IGMP Query messages from multiple sources.
- Avoid using fast leave as this does not offer anything beneficial to the Dante multicast network.
- Avoid IGMP proxies, unless you are CERTAIN you know how it behaves.
- Ensure that ""block unregistered multicast"" is not set on Netgear switches. This blocks traffic that should be allowed (mDNS, PTP).
- Dante devices support IGMPv3.