I would like to build an internal network(to manage iot devices) in which I would be able to connect only to the smartthings cloud.
Do you know what are the addresses of the servers with which the smartthings application for the phone connects?
I am going to use HUB Aeotec and Samsung TV to start with.
I doubt seriously you will be able to get this information in a meaningful way. I would also add that you may need this network to connect to more than you think.
Modern cloud services use gigantic content delivery networks with dynamically reconfiguring networks to deal with availability and traffic constraints. When I worked for one of the largest cloud providers we didn’t give out the endpoint IP ranges for certain services except for the largest enterprise clients and even warned them that we didnt reccommmend they isolate ip ranges because we did not always have control of the changes. So basically, if they did this they were doing so at thier own risk… And don’t call if it breaks.
So is there a specific reason you want to limit the traffic?
I wanted to create a separate network for iot devices only to increase security, if in the future I would like to install additional locks or a courier box, I would feel safer 
So I understand that it is not that simple. Thank you for your help.
P.S.
I am still wondering, the addresses are not assigned to the dns server? can’t use names? Because how does the application know when the address changes and what is the new one to connect correctly?