Some months ago I set up OpenDNS. Since then, occasionally I get slow page loads and pages that redirect to a timed-out opendns page. I would like to see if removing OpenDNS will make browsing efficient again. However, I can't remember how I set it up, nor can I see where OpenDNS is configured.
The guides for setting up OpenDNS mention either the file
/etc/dhcp/dhclient.conf or using the Network Manager. The conf file has no reference to OpenDNS or its IP. The Network Manager doesn't have the OpenDNS IP either.
But I know it is configured somewhere because of the redirects mentioned above, and because https://www.opendns.com/welcome/ reports success.
How do I determine where it is configured?