When switch has "igmp snooping" enabled, I don't understand why VSAN blogs and book require a mrouter or querier to be defined.
From Nexus switch igmp debugs and logs, VSAN will send unsolicited membership reports every 90 secs to group address 224.1.2.3 and 224.2.3.4. This is regardless if we have mrouter or igmp snooping querier configured for the vlan or not. So as long as VSAN is coded to send out membership report periodically, we shouldn't need a "querier" on the vlan to send general/group queries.
As in my testing, I have no igmp querier or mrouter defined for VSAN vlan and all VSAN communicate are good with igmp snooping enabled(by default for NX-OS).
DIA-N5K-02# show ip igmp snooping event-history vlan | i 10.16.127.111
2014 Aug 5 21:31:46.915356 igmp [3465]: [3917]: SN: <127> Received v2 report: group 224.2.3.4 from 10.16.127.111 on Eth1/21
2014 Aug 5 21:31:46.915011 igmp [3465]: [3917]: SN: <127> Received v2 report: group 224.1.2.3 from 10.16.127.111 on Eth1/21
2014 Aug 5 21:30:17.037868 igmp [3465]: [3917]: SN: <127> Received v2 report: group 224.2.3.4 from 10.16.127.111 on Eth1/21
2014 Aug 5 21:30:17.037606 igmp [3465]: [3917]: SN: <127> Received v2 report: group 224.1.2.3 from 10.16.127.111 on Eth1/21
2014 Aug 5 21:28:46.950748 igmp [3465]: [3917]: SN: <127> Received v2 report: group 224.2.3.4 from 10.16.127.111 on Eth1/21
2014 Aug 5 21:28:46.950273 igmp [3465]: [3917]: SN: <127> Received v2 report: group 224.1.2.3 from 10.16.127.111 on Eth1/21
2014 Aug 5 21:27:17.073420 igmp [3465]: [3917]: SN: <127> Received v2 report: group 224.2.3.4 from 10.16.127.111 on Eth1/21
2014 Aug 5 21:27:17.073042 igmp [3465]: [3917]: SN: <127> Received v2 report: group 224.1.2.3 from 10.16.127.111 on Eth1/21
2014 Aug 5 21:25:46.985909 igmp [3465]: [3917]: SN: <127> Received v2 report: group 224.2.3.4 from 10.16.127.111 on Eth1/21
DIA-N5K-02# show ip igmp snooping vlan 127
IGMP Snooping information for vlan 127
IGMP snooping enabled
Lookup mode: IP
Optimised Multicast Flood (OMF) disabled
IGMP querier none
Switch-querier disabled
IGMPv3 Explicit tracking enabled
IGMPv2 Fast leave disabled
IGMPv1/v2 Report suppression enabled
IGMPv3 Report suppression disabled
Link Local Groups suppression enabled
Router port detection using PIM Hellos, IGMP Queries
Number of router-ports: 1
Number of groups: 2
VLAN vPC function enabled
Active ports:
Eth1/21 Eth1/22 Eth1/23 Eth1/27
Po1
DIA-N5K-02# show ip igmp snooping groups vlan 127
Type: S - Static, D - Dynamic, R - Router port, F - Fabricpath core port
Vlan Group Address Ver Type Port list
127 */* - R Po1
127 224.1.2.3 v2 D Eth1/22 Eth1/21 Eth1/23
Eth1/27
127 224.2.3.4 v2 D Eth1/21 Eth1/22 Eth1/27
Eth1/23
