Dante Networks and IGMP Snooping

Dante Networks and IGMP Snooping

Date Updated: October 9, 2019 FAQ #5423
Question:
Does IGMP affect Dante Devices?
Answer:

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. Turning off IGMP snooping will usually solve this problem, but if IGMP is needed then this FAQ can help with configuring the switch properly for use with IGMP and Shure devices.

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.

According to Audinate, IGMP Snooping is vital when:

  • When lots of Dante Multicast flows are used.
  • When Dante is mixed with other Multicast traffic.
  • Using Multicast Dante in 100M networks since bandwidth can quickly be filled.
  • Using critical control devices on the same network as Multicast .
  • Using Wi-Fi on the same network as Dante, otherwise Dante multicast data will flood the Wi-Fi bandwidth.

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 224.0.0.1 asking "What group addresses do you want?" The host(s) respond with a membership report to 224.0.0.2 (or 224.0.0.22) 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. All Dante devices uses IGMPv2, and not IGMPv3.

Set the querier interval short (15 or 30 seconds, or as low as it can go). 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.

In some cases, you may need to 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 may be required for:

  • PTP traffic: 224.0.1.129
  • mDNS traffic: 224.0.0.251
  • Shure discovery: 239.255.254.253
  • Dante Control: 224.0.0.230, 224.0.0.231, 224.0.0.232, and 224.0.0.233.

Additional Tips

  • For small / isolated networks that only have Shure devices, are only using unicast Dante flows without AES67, or when there is an isolated VLAN for Shure gear, you should disable IGMP Snooping.
  • If you experience intermittent audio, then run a Wireshark trace. It may show IGMP Query messages from multiple sources. Contact Applications Engineering for help interpreting Wireshark traces.
  • 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. This blocks traffic that should be allowed (mDNS, PTP).
  • Dante devices support IGMPv2.