Hmmm Interesting...
Howe do you have your B Points connected, ethernet? Any of them wirelessly connected?
Are the B Points connected to a LAN switch?
Do you have DNS Relay enabled on your A Point router?
The main "A" is in my home office, directly connected by Ethernet to my TP-Link router. I have one Point upstairs on Ethernet back-haul (via a couple switches in the path) and the other in the kitchen using the 5Ghz wireless back-haul. Interestingly enough on that unit, the D-Link back-haul shows up as another network name.
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This 2nd point will likely end up on Ethernet too, I'm just trying it out to see how well the wireless back-haul works. We're somewhat lucky in that when we bought this house years ago, we ran Ethernet to most points of the house (bundled with fiber optic too, which has been mostly useless
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I think DNS Relay is enabled, yes. I need to figure out what that really does.
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(Oh, OK, looked it up. I'll probably turn it off and just point to the old router)