Utilisation over 100% on interface running at 100mb

Question

Hello,

I just happened to be looking at some graphs for a gigabit ethernet interface on a cisco switch

Although the interface is gigabit its negotiated with the server at 100mb. However, its acutally showing utilisation OVER 100%... i.e. more than 100mb. How is this possible?

I've checked the interface on the swtich and its definetly 100mb. I've also checked the xmit and recv values in Solarwinds and these are also 100mb...

I've looked at the chart data for 10 minutes intervals (we poll every 10 minutes) and this also shows usage over 100%?

Would be useful to know why this is the case before someone collars me and asks how solarwinds is performing this miracle ;-)

Many Thanks

iasgair · Answer

The default bandwidth of a tunnel interface is 9k. If you add to the config for the interface "bandwidth XXXX" where XXXX = bandwidth in kb then you will get a more accurate figure orion repolls the device. Be accurate or you will get inaccurate results. I had a tunnel interface today  over a 155Mb link and orion claimed it was 81089% utillised!

MavericK5L · Answer

I have this interface here with 7336% utilisation.

considering it is a tunnel interface, does the bandwith command on the tunnel interface affect the interpretation of the data ?

switch Interface (tunnel)9 %  7336%

bshopp · Answer

What version of code are you running on the switch, if an oder version, you may want to look at upgrading the switch.

Different devices behave slightly differently and since we poll on an interval, this can happen.  Devices give us the number of bytes that they send out.  Now whether they up this count as they send out a byte, before, or after and in what block sizes, we don’t know.  However, it is not altogether impossible for a device to show us that it sent slightly more bytes in a given time period than one believes is actually physically possible.