You do not see this is NetBackup, this is at an operating system level / cluster software level. For example, for a Veritas cluster you can run the command: hastatus
Editted to add ...
... apart from nbemmcmd -listshosts which I had somehow totally forgotten about as mentioned below by Marianne ...
Thanks Marianne ...
Please tell us which NBU version and OS on your Master server cluster nodes as well which Clustering software.
'nbemmcmd -listhosts -verbose' should help if NBU was correctly installed as clustered master.
Output similar to the following:
Supporting Storage Foundation and VCS on Unix and Windows as well as NetBackup on Unix and Windows
Handy NBU Links
NBU version: 188.8.131.52
You forgot to mention which clustering software is used...
Have you checked output of 'nbemmcmd -listhosts' yet?