Why is there a big delay before calling?

Question

Asterisk

Began to study Asterisk, there was a following problem.
I created several users and the simplest extensions for two of them, pointing them to each other:

exten => 100,1,Dial(SIP/100)
exten => 110,1,Dial(SIP/110)
exten => _X!,1,Hangup()

When calling, there was a delay of exactly 10 seconds, after which the call began.
I read that such a delay occurs due to the lack of DNS (although I don’t really understand why, it doesn’t appear anywhere for me). Raised BIND, configured the zone, entered the server and clients there. The delay has increased to 20 seconds!
Adding # to the number in the softphone breaks the number and the call does not occur at all.
What is the reason for this behavior and/or what am I doing wrong?
Asterisk 13, running on CentOS 7, clients also on CentOS 7 with Gnome, Zoiper softphones.

Answer 1

At the end of the dialed number, press #
Or change the dialing timeout in the phone

Answer 2

Does asterisk know for sure that the number is three-digit??