Yemble wrote

IGMP Snooping was the cause!  Once it had been disabled on both switches, the radio worked perfectly with both LAG cables connected.

 

Obviously IGMP Snooping does not work properly!

Hi Yemble：

     In my opinion, there are not IGMP Proxy pr IGMP querier in your network. Does your router support IGMP Proxy function?

     Due to you cannot configure IGMP Staic Router port in TL-SG108E, if there are not IGMP Proxy in your network, TL-SG108E will not learn Router port.(Normally, when switch receiver one general queue query packet, the port will be changed to Dynamic Router port directly. But the general query packet be sent from IGMP proxy or querier).

     When switch have not IGMP Router port, the multicast data will not be forward. When you disbale IGMP Snooping function. The multicast packet be forwared as Broadcast packets.

    If you only have one media player, you will not meet any issue when you disbale IGMP snooping.

My router is a LinkSys WRT32X running DD-WRT.  There is no mention of IGMP Snooping in any of the DD-WRT menus, however, there is a Filter Multicast option which is enabled by default.

TBH, I really don't see the point of IGMP Snooping on these SOHO switches, especially if it has the potential to break things in certain circumstances, in this case LAG + Internet radio.  Really, IGMP Snooping should be disabled by default, not enabled, as your average Joe will not have a clue what it is, nor the potential impact on the LAN of having it enabled.  This is especially the case if there is a dependency on some external function which may, or may not, be available, such as IGMP Proxy.  None of this is mentioned within the switch documentation either !!!

Had I been a less technical person, I would have probably returned the radio, at my expense, claiming that it did not work, only then to get billed by the vendor when no fault was actually found!  This is one potential outcome of TP-Link's decision to enable IGMP Snooping by default.