High Sierra has just been pushed out to unsuspecting Mac users but it definitely creates problems with WiFi connections to BT’s Home Hub.
After waking from sleep the connection is lost and will not reconnect without some intervention. Although that’s not quite true, it may connect but will not receive an IP address – it then immediately disconnects and tries again, giving up after several attempts. Sometimes at this point you can manually select the SSID from the menu bar and it works but not always.
After a reboot it may simply refuse to accept the WiFi password saying that authentication failed. I have tried creating new locations in wireless Network Preferences and rebooting the HomeHub. Rebooting the Mac (both MacBook Pro and MacBook Air), tried disabling IPv6 on the Hub, allocating a static IP in the Hub settings, all to no avail.
The best fix so far is to change the wireless settings from using DHCP to a manual configuration. Enter a high address, one that other users aren’t likely to get via DHCP and add 22.214.171.124 to the DNS under Advanced… settings. So you might try:
In >Settings >Network >wifi >Advanced >TCP/IP
Configure IPv4: Manually
Manual IP address: 192.168.1.100
Subnet Mask: 255.255.255.0
Router Address: 192.168.1.254
And in In >Settings >Network >wifi >Advanced >DNS
Click + and add 126.96.36.199
Please leave a comment below if it worked for you.
iOS 11 seems to have similar issues and a fix that I had some success with is to change the wireless SSID of the Hub.
UPDATE Dec 12 2017
There have been some more updates to High Sierra – now on Version 10.13.2 and my latest recommendation for connecting Mac to Wi-Fi is to change the MTU setting.
Go to System Preferences >Network >Wi-Fi >Advanced >Hardware >Configure Manually >MTU Custom >1453
Also change System Preferences >Network >Wi-Fi >Advanced >TCP/IP >Configure IPv4 >Manually