Re: A flurry of notifications at startup

2008/5/30 Murilo Fujita <[email protected]>:
> I imagine everybody that read my e-mail thought "doesn't he know that's
> impossible relay data when the cable is unplugged?"

That depends on the network topology of the system where the agent
is running.   If this box only has a single network interface, then the
agent won't be able to communicate with anything if that link goes down.
But if you're working with a switch or a router, and one link fails, then
it's quite possible that the box can still talk to the NMS, using one
of the other interfaces.   And if there are several NMS systems
configured, then losing the link to one need not affect the route to
the others.

Bear in mind that there's nothing particularly special about linkUp/Down
traps as far as the SNMP agent is concerned.   These are just two of
the many traps that it might be called upon to generate.   It doesn't handle
them in any special way.

An agent will have a list of trap receivers that it knows about.
When it's asked to send a trap, it will try to send it to (some or all of)
these systems.   If there's no network connection to a given receiver,
then those traps won't get sent to that receiver.


>     I know it and I want to know/understand where will appear messages
> showing linkUp/linkDown.

If the link to a given NMS is down, then the trap will never be displayed.
(by that NMS at least).   That's true regardless of whether the trap is a
"linkDown" message, or a "someBuggerHasStolenTheSwitch" report :-)
There's no magic processing here - if the agent can talk to the NMS,
then the trap will be delivered and displayed.  If it can't, then it won't.

Dave

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