What do the UUID's found within the ubroker.properties file require uniqueness against?

What do the UUID's found in the ubroker.properties file require uniqueness against?
Does the UUID need to be unique on the network subnet?
Does the UUID need to be unique within the ubroker.properties file?
Does the UUID need to be unique per machine?
Does the UUID need to be unique for each UBroker?
What is the meaning of Validation Message 8141?

The UUID is used to distinguish between the multiple Unified brokers that can be configured within the same environment.

It is used to uniquely identify a given Broker with the NameServer that is controlling it.  Therefore each UBroker's UUID needs to be unique for the NameServer. To avoid possible issues in the event that Brokers are moved around to be registered to a different Name Server, it's a requirement that their UUID's are unique across time and space within a single computer network. 

In the case of multiple AdminServers running on the same machine, if their components are completely isolated (own NameServer and own Brokers), then strictly they do not need to be unique on that machine as long as Brokers from one configuration don't register with the NameServer from the other configuration.

It is never-the-less a simple task to ensure that the UUID's are unique. Refer to Article  How to create a new UUID for a UBroker in the ubroker.properties   
 

Progress Articles:   

 Origin of Progress UUID (Universal Unique Identifier)   
 Does the GENERATE-UUID function return a universally unique identifier?   
 What are the components of the UUID returned by the WSA?