Re: Can Disman Event MIB monitor remote target's objects?

On 15/01/2008, ERICJ <[email protected]> wrote:
> In DISMAN Event MIB's Trigger Table it defines
>
> mteTriggerTargetTag
> The description says "The length of 0 indicates the local
> system....Otherwise access rights are checked according to the security
> parameters resulting from the tag"
> Is this means I can use Target Tag to monitor different targets?

In principle, yes.

> And from the beginning of the RFC2981 Event MIB at the part of 3.
> Relationship to Other MIBs. It indicates
> "The key extension is the ability to allow alarms to be generated for MIB
> objects that are on *another* network element"
>
> Is *another* network element means *remote* target?

Yes.

> i.e. I can set up entries in Target MIB with the remote monitored target's
> IP address and infos
> and set up mteTriggerTargetTag so that the agent can monitor remote agents
> objects?

Exactly.


> I have tested the EVENT MIB with monitor local agent's objects,and it works
> fine, but I am not sure whether net-snmp 5.4.1 have implemented the function
> to monitor the other remote target's objects?

I'm not entirely sure (as it's some time since I wrote this implementation),
but I strongly suspect not.  I'm pretty sure that it currently only supports
local queries.

Checking the code, the processing of "monitor" directives (mteTriggerConf.c)
sets up the session for retrieving MIB values using either
    netsnmp_iquery_user_session("user");
or
    netsnmp_query_get_default_session();

both of which assume a loopback connection to the local agent.

Creating a monitor entry dynamically (i.e. via SET commands) uses
    netsnmp_iquery_pdu_session( pdu )
which uses the authentication settings of the incoming request,
but again assumes a loopback connection to the local agent.

I don't *think* that the TargetTag value is actually used anywhere.
This is an obvious omission, and it would be sensible to addess this.
If you were in a position to attempt this task, then what you'd basically
need to do would be to adjust the creation of the "session" field in
the event and trigger tables.   This is a standard netsnmp_session
structure (as used in client commands, etc), and is used for retrieving
the values to be monitored.
   If this was set up to refer to a remote agent (rather the local loopback),
then this *should* be sufficient to implement remote monitoring.

He says, not having actually done this, of course!

Dave

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