I would say there most definitely IS a fundamental issue with the SH2.. I've used 3 other routers (2 Asus, 1 UniFi) using the same SSIDs for 2.4/5Ghz without issue. As soon as the SH2 is involved it all goes pear-shaped. Nobody in their right mind would consider this a feature.
BT done gone goofed big-time.
There are numerous devices that rely upon being on the same network in order to sync-up. Presumably their discovery algorithm relies upon announcing to the broadcast address in order to detect one another.
For obvious reasons routers do not generally forward broadcast packets across networks, so devices won't see these packets if they're connected to different WiFi bands.
Google's Chromecast Ultra & Stadia controller seems to be the biggest casualty of this blunder from BT, though there are also a myriad of smart plugs/switches/bulbs that rely upon being on the same WiFi network.
I hope BT drown in the support requests spawned from this inept design decision. Sadly though I suspect it'll be Google that suffers the brunt of the "It doesn't work" returns.
If BT can't reactivate the ability to give WiFi bands their own SSIDs, then they should reconfigure the router to forward broadcast packets between the WiFi bands. (if that is indeed the cause of the problem).
Why do you think the different bands are on different networks? They both are in the 192.168.1.XXX subnet.
@licquorice Good point, is there some kind of AP isolation or firewalling occurring between devices on separate bands then?
It certainly seems like particular traffic types (notably the protocol used for syncing devices) aren't being propagated between devices on different bands.
There's something strange but not sure what. Its not universal or devices on different bands wouldn't be able to communicate between each other at all, but they do. It seems to be smart devices that only have 2.4Ghz capability are unable to communicate with smart phone apps unless the 5Ghz band is switched off presumably thus stopping the phone connecting at 5Ghz.
We had problems with 2.4G freezing and disconnecting, signal strength is good but the quality is only fair or poor because of interference from all the other 2.4 routers nearby. Bought the Smart2 and a disc, set it up and it was fine, nearly all of the kit which could connected using the 5G band to either the disc or the hub and everything was working well. Next day back to the same situation because the hub had reverted nearly everything back to 2.4G. The ability not to force 5G is a serious shortcoming on what would otherwise be a good system. I cannot turn 2.4G off because I have some legacy items which only operate using 2.4G. I suspect the system is just switching to the strongest signal rather than the best quality and fastest signal. Disappointed after spending 3hours setting the system up, 20 minutes connecting the hub and disc and over 2 hours registering all the devices on the new network.
BT Please sort this out.
There is a problem if you have Sky Q as to get it to work reliably you need to split frequencies,
What seem to be happening is that the main Q TV box is dual band BUT only if Sky is the ISP however as you can't split and rename a frequency with the smarthub2 it sees the SSID and sometimes tries to connect using 5Ghz and fails.
It does not effect everyone and for some it works fine once they have turned off smart, if you are using Q mini boxes then it is advisable to move the 5Ghz channel well away from Ch36 as that is the one the Sky mesh uses.
I now have my Sky boxes wired by Ethernet but prior to that I had to turn off 5Ghz to make it work.
This is generally a major issue as a lot of items need to connect to a particular band, especially smart home stuff.
Having to turn off 5g]GHz to force connection to 2.4GHz messes up with stuff that has to connect to 5GHz, and to force that connection you have to turn off 2.4GHz and that then disconnects everything you had to turn the 5GHz off for.
The only solution I can see is to invest in a separate wireless router to enable a separate SSID for both frequencies.
Strikes me as a particularly poor design, almost as poor as not allowing the router DHCP range to be changed from 192.168.x.x to 10.x.x.x
BT can do 1 of 2 things (most likely through a firmware update). They can have the router so that ....
Doubt either of these will happen in a rush in spite how much we're all in agreement of how bad a decision it was to remove the split SSID feature from the SH2.