[mrtg] Re: MRTG Bandwidth Limits?

[cvalin at telespectrum.com]

Jeff,

I ran MRTG on a similar setup at a previous place.
We had ATM over DS-3 and two OC3c (POS) circuits.

Graphing over 110Mb was never a problem.

I might suggest checking CPU activity, particularly if you have some heavy
ACLs on any of the interfaces... if you do, then you might try tuning the
ACL hit on the RSP by tuning it (generally speaking, by placing the heavier
hitting ACL lines at the top of the list).

You did not mention if you might be having buffer/memory problems... I
mention this because you say this happens when you are under a heavier
traffic load.

And BTW (FWIW), querying interfaces for traffic stats alone will not cause
the CPU to see high utilization but make sure you don't have
someone/something else also making queries of your router - this will cause
random performance problems and even times when you might appear to hang the
router (as when doing a snmpwalk).

Christian

-----Original Message-----
From: Jeff Strahl [mailto:Jeff.Strahl at grandecom.com] 
Sent: Monday, November 18, 2002 1:01 PM
To: 'mrtg at list.ee.ethz.ch'
Subject: [mrtg] MRTG Bandwidth Limits?


We have been using MRTG for while now, but it is until recently, that we
have had enough bandwidth on a couple of interfaces that we have identified
a problem.  Now, let me first state, that I do not know if this is a
reporting problem of MRTG, or a problem within our router that we are
polling.

The MRTG version that we are currently running is: 2.9.17

The interfaces experiencing the problem: OC3 POS & OC3 ATM (both reside
within the same VIP4-80, within a Cisco 7507 router with dual RSP4s)

The symptoms of the problem are whenever we hit our peak time, if the
bandwidth exceeds ~110 Mb/sec, the graphs simply draw a flat line _very_
close to zero instead of the true bandwidth amount, for I have connected to
the router during the time that this is seen, and the bandwidth stated via
'show interface POS4/1/0' is consistent with what I would expect to be
passing at that time.  Also, it should be stated, that I do not have MRTG
configured to draw unknowns as zero (one of the reasons that this strikes me
as odd).  On the other hand, the ATM interface simply draws straight lines
whenever this interface exceeds the stated amount of ~110 Mb/sec.  Like I
said, I don't know if this is a problem with MRTG, or the router, but I
needed to start somewhere, and since it appears that the MRTG graphs are
broken, rather than the manual reporting of the router, I decided to start
here.

I appreciate any insight anyone might have with this problem.

Thanks,

Jeff Strahl

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jeff C. Strahl
Sr. IP Network Engineer
Packet Networks
Grande Communications Networks, Inc.
401 Carlson Circle
San Marcos, TX 78666
Phone - 512.878.5465
Cell - 830.620.8176
Fax - 512.878.4284
Email: jeff.strahl at grandecom.com

We will individually and as a Team:
	-	Work cooperatively, delivering what we said we would
	-	Be honest and truthful - showing respect for others
	-	Be easy to do business with - internally and externally
	-	Serve our customers and communities with passion and
commitment
	-	HAVE FUN!
For you, the world.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

--
Unsubscribe mailto:mrtg-request at list.ee.ethz.ch?subject=unsubscribe
Archive     http://www.ee.ethz.ch/~slist/mrtg
FAQ         http://faq.mrtg.org    Homepage     http://www.mrtg.org
WebAdmin    http://www.ee.ethz.ch/~slist/lsg2.cgi


--
Unsubscribe mailto:mrtg-request at list.ee.ethz.ch?subject=unsubscribe
Archive     http://www.ee.ethz.ch/~slist/mrtg
FAQ         http://faq.mrtg.org    Homepage     http://www.mrtg.org
WebAdmin    http://www.ee.ethz.ch/~slist/lsg2.cgi