MRTG bandwidth utilisation not same as sh interface

[Richard Bradfield]

The other day  3rd party supplier ran some stats on our Gigabit link between 2  Cisco catalyst 3750Gs.

now the graphs produced showed only a Maximum output of about 100Mbps ( 5 minute intervals) yet when I do a show interface it shows a lot more always 150Mbps and more. So I did my own Perl script  doing an "sh interface" every minute and then graphed it, and the results were a lot different to the MRTG results.

Questions: I know MRTG uses SNMP  to get the traffic  is there a bug in the SNMP, what OID does it use?

does the "sh  interface" give the correct results?

I would be interested if anybody else has experienced this variance between MRTG and sh interface

[andrew.prince]

On any interface over 100mbs you MUST use 64bit counters, as 100mbs uand below ses 32bit counters.  I have no clue about MRTG - as I use Cacti and it works great.

HTH>

[Richard Bradfield]

Please see the enclosed link to previous conversations. I should have looked into it more before I posted the question

https://supportforums.cisco.com/thread/2032425