wifi connected but No interent in ubuntu 18.04 after upgrade

After upgrade to ubutnu 18.04, the intenet connections both wired and wireless showed that they were connected but the internet was not working.

The issue turned to be wrong DNS server in /etc/resolv.conf

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8) # DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN # 127.0.0.53 is the systemd-resolved stub resolver. # run "systemd-resolve --status" to see details about the actual nameservers. nameserver 127.0.0.53

In the above resolv.conf file add the line nameserver 8.8.8.8

To change the resolv.conf open the file /etc/resolv.conf as root and add the abov line. Save the file and restart networking using

/etc/init.d/networking restart