Re: SNMP newbie question: sysUpTime

Fri, 24 Jun 2005 03:48:03 -0700

Thanks a lot Dave. Things are much clear now.

Unfortunately :( I have a few more doubts:
Consider that my agentX master agent is running for *days*. The sysUpTime accordingly goes into days. I *now* enable my device's port and the device-up trap is sent by my subagent to the manager via master agent.
1. What should be the value of "*LastChange" in this case?
2. If sysUpTime is agent's time (and in net-snmp it is filled by master agent), it will be in days in my trap. "*LastChange" as per its definition will be
    -    this sysUpTime value(which is in days) OR
    -    the uptime of my device's port (which is a few seconds)?

I have a very strange observation (at least to me) to report:
I have used netsnmp_get_agent_uptime() API in my subagent to fill in the value of sysUpTime. My master agent is running for days but my application (containing the subagent) which is currently being tested gets killed and restarted every now and then. I have observed a very strange reading. My sysUpTime and *LastChange parameters display same values of timeticks in all my traps. How can this be possible? Pls note, my master agent and subagent are two separate processes. As per me, this can only happen if after coming up, the subagent is asking for the master agents uptime/start-time? Is this correct assumption and if yes, what purpose does *LastChange really solves?
Or is it that if the manager wants to know the uptime of my managed resource, the *LastChange is *not* the right parameter?

TIA,
Jeetendra

Dave Shield wrote:
On Fri, 2005-06-24 at 09:39, Jeetendra Singh wrote:
  
1. What is meant by "network management portion" in this context?
    
The SNMP agent
  
2. If I have
    -    a managed resource(for ex: device's port status),
    -    a subagent (which is monitoring that port), and
    -    an agentX master agent
Whose uptime will be displayed in SNMPv2 traps sent to manager?
    
The master agent.
  
3. Is sysUpTime redundant in case of SNMPv2 traps, if the trap
definition itself has a "*LastChange" as a trap parameter? Since, the
"*LastChange" parameter is normally defined as "The value of sysUpTime
at the time of the most recent change in state of *", it seems the
mandatory varbind "sysUpTime" and "*LastChange" values will always be
similar in the trap?
    
Not necessarily.
The LastChange value will be the value of sysUpTime when X changed.
The sysUpTime value is the value of sysUpTime when the trap is sent.

If the trap is sent immediately after X changes (probably as a result
of this change), then the two values will be basically the same - yes.
But if the trap is sent some time later (as a result of some other
event), then the two values may well be different.


Dave
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