There’s me blaming the BT Business Hub 3… BT even agreed it was a problem with the hub, but I had a problem with my range extender too, so I did my own PD and came to a different conclusion!
BT Business Hub 3 giving you the IP of 192.168.0.254 for the DNS, so DNS lookups fail, but using IP address or manually configuring the DNS setting to 192.168.1.254 works.
Once I realised the DNS server IP address it was giving was the range extender’s IP address it made a lot of sense, searching around the internet I saw someone mention disabling DHCP on the range extender and that is the fix.
Reset range extender to factory defaults
Plug in Ethernet cable
Manually configure IP address: 192.168.0.10, subnet mask 255.255.255.0, default gateway 192.168.0.254.
Go to the admin page http://192.168.0.254/ login using admin, admin.
Exit Quick Setup if it opens
Go to Network -> LAN
Choose Static IP
IP Address: 192.168.0.254
Subnet Mask: 255.255.0.0
Go back in again.
Go to DHCP -> DHCP Settings
Choose DHCP Server: Disable
Now go configure the Wireless options etc.
Once complete disconnect the cable and try the wireless, it should work now.
This is probably an issue for the BT Home Hub too, but I don’t have one to validate it, regardless, you should turn off the DHCP as shown above, the BT Home Hub is your DHCP server.
Hope that helps.