Last Saturday, one of our laptops running Ubuntu 16.04 zesty suddenly couldn’t get on the Internet anymore. It connected to the router and could ping IPs, but DNS lookups failed, so no browsing was possible. After researching online, I found out that Ubuntu changed to a new type of DNS resolver (systemd-resolved) in zesty, and this causes issues for some people. It seems we were affected by this, although i have absolutely no idea why the problem surfaced when it did after working just fine for weeks after upgrading to zesty.

Anyway, here are the instructions that ultimately fixed the problem:

  1. find out the current IPs of your ISP’s DNS servers (log in to your router, check tab Internet)
  2. edit resolved.conf: sudo nano /etc/systemd/resolved.conf. In the section [Resolve], add the DNS server IPs

    then save and exit.

  3. restart the services with:
    sudo systemctl restart systemd-resolved
    sudo service network-manager restart