DVS, Mac, and IGMP3

[Peter Baird]

Just found out about this today. The reason I'm putting it up on a Pro Tools forum is that I know a lot of us use Dante Virtual Soundcard to connect Pro Tools to a Dante network.

Over the weekend I was mixing music on an awards show. We used a Dante network to connect two RIO 32s, two CL5s at FOH and Monitors, and I had a CL3 in the truck shipping the music mixes to the production desk. It all worked great except...

I ws trying to use DVS and my MacBook to run Nuendo Live as a virtual soundcheck. But no matter what I did, the laptop refused to pass audio and had a red light in the clock window in Dante Controller. Ben, the contractor's system tech, brought his Windows machine in the truck and hooked it up, and Shazam, no problems at all. The next day I brought in a different MacBook (also with DVS) and had the same issue. Since I've used DVS successfully many times in the past on the laptop, I suspected it must be some kind of DVS/Sierra issue, so I started a case with Audinate. Here's their reply:

Hello Peter,
It’s not a Sierra and DVS problem. That issue if we can’t sync to the master clock comes from an IGMP version 3 incompatibility in your network. If you disable IGMP, it should synchronize just fine.
There is probably an IGMP version 2 device in the network that is causing OSX to discard join requests from the IGMP querier.
You can read more about it here:
https://serverfault.com/questions/81...ership-queries

Thank you,
Brett Silver Begani
Audinate Customer Support
https://www.audinate.com/support
1-503-224-2998 x229

First of all, thank you Brett. Second, jeez, another thing to keep track of on the network switches (and that list is getting very long). What I understand from the above, and puzzling over the link, is that there was probably a switch somewhere in the network configured IGMP-2 and the Mac was doing exactly what it was supposed to do, ignoring all the IGMP-3 requests on the supposition that the IGMP-2 device might not be able to keep up.

Now I'm certainly the last person remotely qualified to have an opinion on this, but my understanding of IGMP snooping is that it's an important tool to keep multicast flows under control and reduce multicast "flooding" over a network. In light of this I'm unsure whether to disable it or go through the whole exercise of checking the settings of every switch in the network to make certain they all support IGMP-3. (In Cisco 300 switches the IGMP snoop settings are under the Multicast tab, BTW.) Yamaha says:

Dante supports both IGMP V2 and V3, but all switches in the network should be running the same version. So if the network includes switches which support only IGMP V2, be sure to select "IGMP V2" as the IGMP querier version.

I hope it's all clear to everyone now. Good luck.

Peter

[Peter Baird]

Further information from Brett at Audinate about disabling IGMP snooping:

If you’re under 80mbps, it won’t have any effect on a gigabit connection.
If this is an isolated network, you shouldn’t see any problem with all ports having access to the multicast.
If it is a shared network with other traffic, then you will need to investigate what problems can arise from turning off the IGMP snooping.

As I said, I'm not really qualified to comment about network settings. But he is.

Peter