| It depends (as usual :-).
'Normally' the Hub Manager is the only manager. On the 900 backplane,
the management channel is actually a star with the Hub Manager at the
center rather than a bus; this is more reliable because a bad module
can only disable management for its own slot.
In order to provide DEChub 90 compatibility, the Hub Manager can allow
a DECbridge to become the bus master, and therefor a DECagent can act a
the agent for the hub (though it will not recognize all the 900
modules). To do this, just don't give the Hub Manager any IP address
(either for In-band or the OBM port); since it can't be the agent for
the hub without one, it will allow a DECbridge (or a V2.0 DECagent) to
become 'bus' master, and will forward messages on the star to emulate
the DEChub 90 bus. In this mode the 900 looks like an 8-slot 90; there
is no way to use the LAN hopping, manage the 900 modules through the
hub, or use any other 900 management capabilities.
This feature allows existing DEChub 90 customers using the DECagent 90
and V1.1 HUBwatch to upgrade one thing at a time rather than everything
at once.
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