What is the best way to configure APM components in the overall communications between other APM components, i.e. Enterprise Managers (EM's) and agents?
All current supported APM environments
Basically you can configure the components to communicate via hostname or IP address, though you would need to determine which is more reliable for your needs:
Using a Fully Qualified Domain Name (FQDN), resolved by DNS, would automatically cover any server IP Address changes that might occur. Of course, the DNS lookup performance for hostname -> IP Address resolution needs to be successful to avoid any communication delays.
Using FQDN would be beneficial for setting up failover EM's where the FQDN lookup automatically handles the change in IP address at failover time. Alternatively a Virtual IP Address (VIP) approach could be used for that.
A FQDN may not be appropriate if you have firewalls between components where only 1 specific NIC can be used to communicate between components, i.e. the IP Address of that NIC needs to be explicitly used.
For EM->TIM communications, this setup requires IP Address use.