iCloud Keychain issue on iPhone

[donawalt]

HI all, I guess this is the right place to put this message, but it affects other devcces with access to iCloud keychain.

I can't say I understand all of this but - for some testing and isolation, I set up a guest network that my router supports, separate SSID from the main network. I gave it a unique password. I 'forgot' the main network on my iPhone 16 Pro Max, turned off "Auto join", and then connected it to the Guest network for my testing. All was good.

Hours later, I happened to stumble on the fact that 2 MacBook laptops, and a HomePod are now also connected to the Guest network! I know the password is stored in the iCloud keychain, but how could this happen? I see on my iPad that the Guest network is in the section "My networks" as well.

Why would they have connected to the Guest network? Is there a way to just have the 1 device on the Guest network and not others? Or won't that work if you are logged into the same iCloud account?

 

[iStorm]

iCloud Keychain also syncs Wi-Fi networks (SSID and password). You would probably need to turn off Auto-Join for those devices you don't want to connect to the Guest network. (If you forget the network, then you're also removing it from iCloud Keychain, and all your other synced devices would eventually forget it too.)

 

[donawalt]

Thanks @iStorm kinda what I figured. I don't think HomePod has a AutoJoin setting though. The thing I don't understand is not how devices know this info (SSID as a known network, password), but hy they jumped off the main network onto the Guest network. None of the Macs or HomePod has moved today.

I could understand if it was a mobile device out of the house that came back in, and saw a beacon from the GN first. But why in these cases I wonder?

 

[iStorm]

Yeah, that does seem interesting. Just a theory - when you 'forgot' the network on your 16PM, you probably inadvertently removed the rest of your devices from the network as well. Then when you connected to your Guest network, the new Wi-Fi info eventually synced to your other devices (via Bluetooth?). Not sure about the HomePod though, maybe it "fixes" itself or syncs via Bluetooth as well.

 

[donawalt]

It wasn't all the devices on the network, just those 3 besides the one I was working with. Very strange.Probably guest networks on these routers have all kinds of security holes lol.