PTP Dante not working over stretched vlan

[Jeff_V]

The situation at a customer is as following:
They use a Meraki Core: (1)410/16
With a couple of acces layer switches: (6)250/48's

The customer provided us with a couple of vlans (one of these for dante communication)
When opening wireshark all traffic is as expected except PTP.
there is ptp traffic (Multicast on 239.0.1.217) only on one switch. 

In Dante controller we see a different Master per Switch elected.

Other multicast traffic like mDNS does work correct.

We are looking for a solution in this case,

Is there a way to turn off igmp per vlan or is there a better solution for this problem.

Kind Regards,

[PhilipDAth]

The multicast code is much better in the 10.x firmware on the switches.  I would be tempted to move to the 10.x code.

[m_Andrew · Accepted solution]

Adding to what's already been mentioned:

If your application is making use of multicast inside an L2 domain (single VLAN) that stretches across multiple switches, and IGMP snooping is enabled on the switches (the default), you will need to be sure that an IGMP querier exists inside the VLAN. If there is no IGMP querier, it can be possible for the multicast streams to be black-holed when they traverse multiple L2 switch hops.

IGMP querier configuration documentation can be found here:

https://documentation.meraki.com/zGeneral_Administration/Other_Topics/Multicast_support#IGMP_Querier

For the most optimal forwarding of the multicast streams (avoiding unnecessary forwarding), it will be best to enable the querier on the switch as close to the multicast sources as possible.

NOTE:

It is not necessary to enable an IGMP querier on your Meraki switches if another non-Meraki device is connected inside the VLAN that is acting as the querier. If multiple queriers are enabled in a VLAN, only the one with the lowest source IP will be actively querying.