Note:  The switches are actually the SG2008 v4.20

I am experiencing what I perceive as a multicast problem on one of my VLANs.  The setup for the VLAN is very simple as shown below:

In this configuration the ISP router (which provides IPTV services) is connected to an access port on the attic switch. VLAN 200 is then trunked with other VLANs to the Den Switch where the decoder is connected to an access port.  These two access ports are the only VLAN 200 ports in the entire network.

Several days ago the TV connected to the decoder began to experience video freezes and, at times, some pixelation.  This usually indicates multicast flooding and requires that IGMP snooping be enabled.  This setup has been working for months without any issues which makes it hard to understand why it is happening now.  Recently, the switches were upgraded with new firmware and the whole network is using an OC300 controller with the latest V6 firmware.

When the issue first presented itself, my first thought was that the decoder had a problem.  It was factory reset but the problem continued.  Likewise, the ISP’s router was reset but did not fix the problem.  The decoder was then taken from the den area and connected directly to the ISP’s router.  The problem disappeared and the decoder works perfectly meaning that there is a problem somewhere in the switches.

In the switches, I have disabled STP/RSTP and loopback detection.  I have reverted back to the previous firmware.  IGMP snooping and MLD snooping are enabled in the VLAN configuration.  In the same configuration, I enabled QoS Queue and set it to Queue 7.  I really don’t know what else to check or configure.  In the controller’s Configuration Result, under Incompatible, it states for the SG2008 switch ports “The device does not support the 802.1p Priority and Trust Mode configured in this configuration entry.”  That tells me QoS might not be a fix but I am unfamiliar with QoS settings.

Does anyone have any ideas on what I might check or configure?  Any help would be most appreciated.