[mrtg] Re: Dell Powerconnect 3024 -- SOLVED (Negative Request IDs )

[Horner, Ben]

Hi Dan,

I am Systems Admin for a multimedia company and am running MRTG on our
switches and routers successfully.  We recently bought 2 new Dell 3048
PowerConnect switches which I am TRYING to get MRTG going on.

I have read all your posts about the problem with SNMP with the Dell
switches, however, I don't know Perl and so didn't fully understand your
solution to the problem.  I understand that the problem is the negative
numbering in the request ID field but how do you change the request ID
number?  How do you get it to accept a negative request ID????

If you can help with this I would really appreciate it!

Thanks
Ben

-----Original Message-----
From: Dan Mahoney, System Admin [mailto:danm at prime.gushi.org]
Sent: Saturday, 18 January 2003 12:19 PM
To: mrtg at list.ee.ethz.ch
Cc: simon at switch.ch
Subject: [mrtg] Dell Powerconnect 3024 -- SOLVED (Negative Request IDs)




Okay, I found the problem with the 3024's and presumably the 3048's.  I've
noticed that whenever I had the error, the request ID was a negative
number.  It's not listed in the configuration options for MRTG, but
there's a (relatively new) option in the snmp-session library...  As
follows.

SNMP_Session.pm 0.93: There's a new variable
$default_avoid_negative_request_ids. If it is set to a non-zero value,
newly created SNMP_Session objects will be configured so that only request
IDs in the range 0..231-1 will be used. This is needed to work around a
bug in several SNMP agents. If you sometimes see requests fail, and the
error message always shows a negative request ID when that happens, please
notify the vendor of your agent of the bug. While the vendor fixes the
problem, you can set the variable mentioned above to work around the bug.
The problem has been described in a few mails on the mrtg-developers
mailing list that can hopefully be found here in the archive.

I'm including as much information as possible in the hopes that as many of
us can scream at Dell for our frustrations, and also so that the archive
can hold complete info (IF anyone can locate it).

For those of you that feel your problem has been solved by tweaking
timeout, remember that MRTG doesn't graph gaps, you'll just see
extrapolations or plateaus.   This here is the culprit:

Hardware Version:  PC-3024-00
Boot ROM Version:  4.5.2214
Software Version:  5.2.5.2194

Setting the avoid_negative_request_ids variable (i just hardcoded it in
the mrtg-included-version of the library) seemed to work for a while.

But I still saw negative requests.  I searched the code for it, and I
didn't see the variable see it appearing often, but I don't understand the
coding style, so I'll ask.  How does the library determine that a request
isn't negative?  Does it only select from a positive range, or does it
multiply any negative version * -1?

I thought for a while about the consequences, then I said "what the hell"
and tweaked it in my site_perl's copy of pm.  Everything *seems* to work
now, but will this be the case or does the "avoid" code only do merely
that (i.e.  is there still a chance at a negative request ID?)

Ah well, things appear to be working smoothly-er here.  (Is that even a
word?).

On to the next problem.

What to eat for dinner.

-Dan

--

Pika Pika Pika!

-Pikachu, of Pokemon fame.

--------Dan Mahoney--------
Techie,  Sysadmin,  WebGeek
Gushi on efnet/undernet IRC
ICQ: 13735144   AIM: LarpGM
Site:  http://www.gushi.org
---------------------------


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