This could be caused by something sending out a large number of broadcast or multicast packets, or packets to an unknown MAC address, which the switch would sent to all ports as it doesnt know on which port the true destination is located. You would see spikes on all the switch ports for the VLAN. Possibly you have something doing massive amounts of broadcasts, or something that is trying to scan the subnet by pinging all IPs resulting in many ARP requests going out?
Steve Steve Shipway University of Auckland ITS UNIX Systems Design Lead [email protected] Ph: +64 9 373 7599 ext 86487 ________________________________________ From: [email protected] [[email protected]] on behalf of Paul Macdonald [[email protected]] Sent: Friday, 18 March 2011 3:18 a.m. To: [email protected] Subject: [mrtg] similar graphs Hi, I am using mrtg for simple bandwidth monitoring on our cisco switches. The graphs on one switch appear to have very very similar peaks across 4 or 5 ports, although the totals and the axis are quite differnet. Each of the servers on each of the similar ports performs quite different tasks so its very unlikely that they would have peaks at the same times. Has anyone encountered anything similar, should i suspect hardware problems on the switch? Typical mrtg targets are of the form : (64 bit counters). Target[x.x.x.x_10111]: ifHCInOctets.10111&ifHCOutOctets.10111:[email protected]:::::2 If i run some large transfers through any of the ports these show up normally on the appropriate graphs, and the similarity disappears as expected under normal usage the graphed load is as expected but the similarities across these ( 4 out of 24 ) ports seem very mysterious and unexplained. I plan to swap the feeds at some point to see if the behaviours follows, but have not done this yet.. thanks Paul. -- ------------------------- Paul Macdonald IFDNRG Ltd Web and video hosting ------------------------- t: 0131 5548070 m: 07534206249 e: [email protected] w: http://www.ifdnrg.com ------------------------- IFDNRG 40 Maritime Street Edinburgh EH6 6SA ------------------------- _______________________________________________ mrtg mailing list [email protected] https://lists.oetiker.ch/cgi-bin/listinfo/mrtg _______________________________________________ mrtg mailing list [email protected] https://lists.oetiker.ch/cgi-bin/listinfo/mrtg
