H3C S5120-EI Series Operation Manual page 1097

Network requirements
The local clock of Switch C is to be used as the master clock, with a stratum level of 2.
Switch C works in the multicast server mode and sends out multicast messages from
VLAN-interface 2.
Switch A and Switch D work in the multicast client mode and receive multicast messages through
VLAN-interface 3 and VLAN-interface 2 respectively.
In this example, Switch B is a L3 switch and it must support the IGMP function.
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