Wifi discs disconnect as soon as plug ethernet switch into port of BT Hub

[savage588]

I have hooked up an 8 port ethernet switch in my loft to provide wired internet dropping down into the 4 bedrooms. I have 3 black BT wifi discs  evenly spread around the property. Now this setup has been working fine for 6 months however all of a sudden my 3 wifi discs have started flashing red.  When trying to use the BT app to reconnect, the app cannot locate or sync my hub. Tried connecting discs without the hub but no success. Had BT engineer out, he replaced the hub and synced the discs back up. All was working fine until plugged the the ethernet switch back into the port on back of hub and app loses sync with the hub and discs lose connection, unplug the switch and all works again??

Any ideas??

[Keith_Beddoe · Accepted solution]

@savage588 

I suspect that you may have created an unintentional Ethernet loopback. That can happen if one of your wired computers is also connecting via wireless.

You may be able to identify which one, by disconnecting all of the connections to the switch, apart from the one that is connected to the Ethernet port on the disk.

Then connect each one, one at a time, until you find the one causing the loop.

Other loopback conditions can be caused by having more than one Ethernet connection from the home hub, going to the same LAN segment. This can happen with powerline adapters.

[savage588]

Cheers Keith, I'll have a look