I have just completed a reformat and fresh installation of macOS Catalina (10.15.7) on my 2012 Macbook so it can be passed on. The Internet is not working, though.
An identical 2012 Macbook is working fine as are other machines on the same network, so we assume our Internet is OK. We have checked the network cable on the other 2012 Mac - it is working. The problem exists regardless of whether it is cabled or Wi-Fi. On the machine in question:
ifconfigreturns an IP address and the correct gateway.
- Other machines on the LAN can ping the problem machine.
- All settings (other than appropriate MACs/IPs) are identical to the other 2012 Mac which is working ok.
- The router/gateway IP can be pinged.
- The external IP address provided by our ISP and as identified on the router/gateway can also be pinged.
- Neither of the DNS addresses provided by our ISP can be pinged.
- Neither of the Google DNS IPs can be pinged 188.8.131.52 or 184.108.40.206
- Time and date are correct.
nslookup www.apple.com 220.127.116.11times out with the response
no servers could be reached. Local windows machine returns a result.
- I have tried turning it on and off again.
- Problem machine works fine on my phone hotspot.
- It can reach the Router admin page.
- Restarting the router doesn't help and firmware is up to date.
- BUT unplugging the router does!