Change of DNS and NTP servers

Hi valerixo21 , 

If you need to configure DNS / NTP it's highly recommended to configure or add it on each guest not the host because guests seem to be different independant boxes or Virtual machines, I am talking about vCMP deployment not for normal bigips. 

> To add NTP , Follow this Article: 
https://my.f5.com/manage/s/article/K13380   >>> CLI 

https://my.f5.com/manage/s/article/K3122     >>>GUI

For your query about the impact , when you navigate any Article documented from F5 you should keep your eyes for this statement " Impact of procedure: Performing the following procedure should not have a negative impact on your system." 
That's mean there is no service interruption or negative impact on your system , and adding NTP servers will not make any impact. 

after fininshing your NTP Configurations , use this Article to verify that your NTP works well  : https://my.f5.com/manage/s/article/K10240

> To Configure DNS servers : 
use the below Article to add your DNS servers : 
https://my.f5.com/manage/s/article/K13205 

It shouldn't intrrupt your services as well. 

I hope this helps you 🙂