snmp agent as an agentx subagent

[Dave Shield]

> Interesting point. AgentX++ does not allow registrations for
> MIB objects that an AgentX++ master supports itself. All 
> AgentX registrations that interfer the master`s non AgentX
> (local) registrations will be blocked (registrationNotAllowed).
> 
> I designed it that why, because I thought it would not make
> sense to override such MIB modules like the SNMP-TARGET-MIB
> by a subagent, because that modules is used within the master 
> to send away traps.

In general I would agree.

It's perhaps not quite as cut-and-dried as that, since the
master agent could still interrogate a sub-agent hosted Target
MIB (using AgentX requests) to determine where to send traps.

  But there are other MIBs (such as the SNMP statistics) that
would be harder or impossible to implement within a subagent.
These can really be only sensibly implemented within the master
itself.

  And even with the Target MIB, it's easier if this is local
to the master agent.


> Does the UCD master agent allow the overriding of any 
> registration even if it is local? Including the target MIB,
> USM MIB, and VACM MIB? 

The approach that the UCD implementation has taken is to
register the "master-only" MIBs at priority level 1, rather
than to prevent subagents registering them at all.

Currently this is only applied to 'sysORTable', but my
intention has always been to extend this to various other
similar MIBs. But it might well be more sensible to bar
such subagent registrations altogether.

  It hasn't been too much of an issue up to now, since the
UCD AgentX support is still very much experimental.  But as
soon as I've got my current projects out of the way, I'm hoping
to pick up the AgentX stuff again.  At which point such issues
would need to be thrashed out among the UCD coders.

Dave