5 second resolving delay

Your problem is described on http://udrepper.livejournal.com/20948.html, and is caused by a parallel lookup on both IPv4 and IPv6 which doesn't work together with some DNS servers and firewalls.

It can be fixed by adding "single-request" to the options in /etc/resolv.conf as the link above mentions.

If you prefer NetworkManager service, then using nmtui/nmcli is better. (the following cmds tested on centos7)

change setting (for those who suffering from 5s DNS delay problem)

nmcli con modify YourConnName ipv4.dns-options "single-request-reopen timeout:2"

you can find YourConnName by executing : nmcli con show

apply setting

nmcli con down YourConnName ; nmcli con up YourConnName

P.S. change the setting to default, which is empty

nmcli c m YourConnName ipv4.dns-options ''