In our environment (lots of CentOS 7 VMs), we routinely encounter the oft-discussed issue where name service lookups result in a 5 second delay as a request times out, even on "successful" requests. As others have tried, we've disabled IPv6 (not used in our internal environment), and it didn't completely resolve the issue. Searching through the forums, we found the suggestion to add "options single-request" to /etc/resolv.conf; this does seem to fix the problem, but manual edits to resolv.conf are routinely overwritten by NetworkManager.
I've searched around, but I can't seem to find a place in nmtui or nmcli to specify this so that NetworkManager knows to include the option when it rewrites the file.
Am I missing something obvious? Is there a way to set this somewhere else? Is there another, preferable fix for the issue?