I have a problem with a new, complex system for managing ethernet 
connected solar inverters and the problem may well be down to missing 
multicasts from a BT home hub.
The German manufacturers insist there is nothing wrong but do not have 
any ideas. It is likely that there is a handful of similar setups 
working in the UK but not this one.
The system consists of 3 solar inverters and a controller that is 
connected with a switch which is also connected to the local network and 
ultimately the internet. The inverters and the controller connect to the 
company server and upload data. There is a local configuration programme 
which runs on a PC and connects to each of the inverters. Everything 
works as expected network wise.
The system has a "heartbeat" so that each inverter gets a message every 
second to continue. If the message does not arrive the inverter 
automatically shuts down and this is this function that is not working.
Buried in the documentation I found the following:   "For the correct 
function ..... all network devices used must support the IGMP protocol, 
minimum
required version 2. (IGMP V2)"
I had to look up IGMP having not come across it before. I originally 
thought that the heartbeat signal comes from the controller and so only 
the switch should be required to support IGMP. I couldn't find any 
reference in the switch documentation but assumed that a brand new 
switch would support it. I tried two other switches that were to hand 
and had the same results.
My latest thought is that the heartbeat may actually come over the 
internet from the company server. That would mean that the network 
router would have to support the IGMP protocol. The network router is an 
oldish BT home hub. This thought has just occurred and I cannot get at 
it to look because it is some miles away.
For anybody that has followed what I have been trying to describe, do BT 
Home hubs support IGMP? is there something in the configuration that 
enables/disables it and is there a test that I can do to verify it?
Thanks for your patience, I hope the above was relatively clear.
Roger
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