I ran the betas of macOS Sierra without incident but recently began experiencing random wi-fi drops with the GM. When I was connected to wi-fi the speeds were unusably slow.
I took the usual troubleshooting steps of toggling wi-fi off and on, restarting the machine, creating a new location in Network Preferences – even manually configuring DNS to use Google’s public servers. Nothing worked. Then I ran across this article at OSXDaily.com that suggested specifying a lower custom MTU setting of 1453. That seems to have done the trick.
Here are the steps I took that fixed my wi-fi issues (see the full article for additional troubleshooting steps):
- Pull down the Apple menu and choose “System Preferences”, then select “Network”.
- Choose Wi-Fi from the left list in the Network panel.
- Pull down the “Location” menu and select “Edit Locations”.
- Click on the [+] plus button to create a new network location with an obvious name like “Custom WiFi Fix”.
- Use the Network Name dropdown menu and select the wi-fi network you want to connect to.
- Now choose the “Advanced” button in the corner of the Network panel.
- Go to the “TCP/ IP” tab and choose “Renew DHCP Lease”.
- Now go the “DNS” tab, and under the “DNS Servers” list section click on the [+] plus button, adding each IP onto its own entry: 8.8.8.8 and 8.8.4.4 – these are Google Public DNS servers that are free to use by anyone but you can pick different custom DNS if you’d prefer to set custom DNS.
- Now select the “Hardware” tab and set the “Configure” option to “Manually”, then adjust the “MTU” option to “Custom” and number to “1453”.
- Now click on “OK” and then click on “Apply” to set the network changes.
- Exit out of System Preferences and open an app that uses the internet like Safari, your wi-fi should work great now.
Thanks to the guys over at OSXDaily for putting this together. It’s been a great help.