[rrd-users] Re: Rollover problems on high bandwidth?

Alan Nichols Alan.Nichols at EBay.Sun.COM
Fri Oct 22 03:37:38 MEST 1999


I assume that will all these tools you are polling the inOctets and outOctets
counters on the router.  These counters are 32bit counters, and will roll over
at least once every 5 minutes if more than @115Mbits/sec traffic is going 
through the interface.

Do the math yourself:

	2^32 = 4294967296 (bytes)
	4294967296 / 300 (seconds) = 14316557.65 bytes/second
	14316557.65 * 8 (bits in byte = 114532461.23 bits/second =114.5Mbits/sec

So, what you need is to monitor different variables.  If your box supports
SNMPv2, it should support the ifHCInOctets and ifHCOutOctets variables, which
are 64 bit versions of the same things.

>From: Paul Fischer <paul.fischer at cwusa.com>
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>To: "rrd-users at list.ee.ethz.ch" <rrd-users at list.ee.ethz.ch>
>Subject: [rrd-users] Rollover problems on high bandwidth?
>X-archive-position: 426
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>X-original-sender: paul.fischer at cwusa.com
>X-list: rrd-users
>I'm using RRDTool 1.0.7, MRTG 2.8.8, gd-1.6.2, libpng 1.0.3, and zlib 1.1.3
>on Solaris 2.6 with perl 5.004_04 and the latest version of 14all.cgi. 
>I am polling an ATM OC-12 interface on a Cisco 12012 router which is
>passing ~300 Mbps and has been for about 40 minutes. However, my 14all
>graph is showing a max traffic rate of 121 Mbps and current usage of 80
>Mbps. However, when I look at the interface stats, I clearly see over 290
>Mbps. Any idea why this might be rolling over? Is anyone else running
>traffic at these rates?
>Paul Fischer - Sr. Network Eng. - Cable and Wireless Web Hosting
>Author "Configuring Cisco Routers for ISDN" - Publisher McGraw-Hill
>http://paul.tibex.com - paul.fischer at cwusa.com - (703) 292-2123 (v)
>(703) 609-802.3 (cell) - (703) 292-2461 (fax) - Danger Will Robinson!!
Email: Alan.Nichols at Sun.COM	Phone:(408)276-1306
Pager: Alan.Nichols at pager.ebay.sun.com	or (650)940-0687
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