Why do IPTVs suddenly stop playing video when IGMP Snooping is enabled?

JasonTsai

A common misconfiguration occurs when the port of an uplink switch has been configured to "Immediate Leave". Keep in mind that "Immediate Leave" is a setting designed for ports that are directly connected to your IPTV's set-top box.

In a common IPTV solution where all ports are set to "normal leave", the IPTV's set-top box sends an IGMP leave message towards the Querier every time the IPTV's channel is changed.  



After the switch in Querier state receives this leave message on one of its switch port, the switch sends a Group Specific Query (GSQ) to all devices under that port. If no other IPTV's are watching this channel, the switch in Querier state will stop streaming this channel down that switch port. 

ALTERNATIVELY, if "Immediate Leave" is configured on an uplink switch port, the Querier does not send any GSQ down its switch port after it receives a leave message. Instead, the "Immediate Leave" port stops streaming this channel right after receiving the leave message.



The consequence of this is that IPTVs watching the same channel under the "Immediate Leave" port will suddenly lose its stream.