How to find out why a program starts in centos only after 40 seconds?

Question

linux

Good afternoon
A small server under centos 7.6 on the xfs file system with asterisk + freepbx slows down when starting programs. The delay is always the same.
I try to login via ssh, enter login ... and wait 40 seconds before the password prompt appears. I start mc ...and wait 40 seconds before it starts. In the freepbx web interface, I click on any link ...and wait 40 seconds.
At the same time, commands such as ls, cd, cat, etc. work instantly without any delay.
The problem appeared after I changed the ip-address of the server to a different subnet.

Answer 1

dns check