Randy Watson once sang the cloud is our future and so it is especially on Google Cloud which I love dearly. Anyway putting Documentum onto a cloud platform seems like a good idea and avoids all sorts of corp IT complications.
The Docbroker provides the address of a Docbase and its port. If the Documentum server is running on an cloud server it will be running on an internal network address. You need to translate that and its easy enough. If you dont you will probably get this helpful message:
[DOCBROKER_CONFIGURATION] secure_connect_mode=dual [TRANSLATION] ' Documentum Ports port = '47625=47625' port = '47626=47626' host = '45.324.124.45=10.156.0.2'
So what you need to do is provide the internal and external IP address and port. The format here is; external=internal