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Today, I installed Security Update 2017-001 for Sierra 10.12.6 and my WiFi is unable to get a DHCP IP address off anything any more. I trashed the usual suspects in /Library/Preferences/SystemConfiguration:

  • com.apple.airport.preferences.plist
  • com.apple.network.eapolclient.configuration
  • com.apple.wifi.message-tracer.plist
  • NetworkInterfaces.plist

I rebooted to find nothing had changed. I tried setting up a new network location and connecting to a local WiFi access point but DHCP can't get an IP. I also reset SMC and NVRAM.

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    May seem like an obvious questions, but do other devices on your WiFi get an address? What if you set an IP manually? Can you get connected? Is it that you cannot connect to WiFi at all (can't associate to the AP) or you can connect, but no DHCP? – Allan Nov 3 '17 at 9:37
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    I would get away from trashing things in library and try to use defaults delete more surgically. The preferences system works very differently now so messing with “the usual suspects” can cause more problems than it might cure. – bmike Nov 3 '17 at 11:16
  • The whole network otherwise performs exactly as it did and is in no way changed by my mac's upgrade. My wife's mac, which was not upgraded, remains functional and will happily reconnect via DHCP to the same access point. – frumbert Nov 4 '17 at 10:08
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I like to remove the network interfaces entirely if someone manually delete plist files or changes things in the library directly and then restart to give the system a chance to recreate the files if it can. Especially on Sierra and later since the preference files aren’t canonical in most cases and the settings persist in a database and get flushed back to disk periodically when the defaults system commits a change.

  1. Remove WiFi interface from all locations (if you have network locations)
  2. Restart
  3. Add in the wirelesss network connection in system preferences

If that doesn’t work, next is two items. You may want to check the network with another device or two - the Mac update could be coincidence and not causal. If the network is working, then you’ll want to look at things other than the core os.

Firewall (little snitch), anti virus (eset or Kaspersky), vpn software and anything that adds extensions or network modifications.

  • Removed and recreated networks and rebooted. Can't get an DHCP address, so I set an IP that I knew was on the range my router could hand out (but is above what it normally will), set default gateway and dns to point to the router - and internet works again. Re-enable DHCP, won't pull an IP address. Took machine to my office and repeated. Able to set an IP address / subnet etc, but no DHCP. Other machines on the same network pull DHCP just fine. No firewall or antivirus or vpn active... What changed? I installed the update and rebooted, that's all. Hmm. – frumbert Nov 4 '17 at 10:12

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