Interface Statistics

[Michael W. Williams]

I have a pair of Cisco Catalyst 3750-X switches in a STACKED configuration.

I need to determine the peak utilization of the seven VLANS I have defined.

I have used the "SHOW INTERFACES" command to dump the interface counters to the console (see below).

I am planning to use the values in the "InOctets" column for my utilization computations.

I need to understand how the InOctets values are compiled.

Here are some questions I have about the "InOctets"

  1) Are the values accumulated over a standard interval?

  2) Do the counters need to be RESET or CLEARED periodically?

  3) Is there a way for an interface utilization report to be produced on a recurring basis?

Switch#show interfaces counters module 2

Port            InOctets    InUcastPkts    InMcastPkts    InBcastPkts
Gi2/0/1                0              0              0              0
Gi2/0/2                0              0              0              0
Gi2/0/3                0              0              0              0
Gi2/0/4                0              0              0              0
Gi2/0/5             4022              0             29             26
Gi2/0/6             7148              0             58             38
Gi2/0/7       1173826565        2509309          58909           3709
Gi2/0/8        263543826        4032277             10           4477
Gi2/0/9        122777027        1796842              2          67622
Gi2/0/10               0              0              0              0
Gi2/0/11      2274035573        2979868              0            439
Gi2/0/12      2257011627        3215977              0            430
Gi2/0/13               0              0              0              0
Gi2/0/14               0              0              0              0
Gi2/0/15        17879638          16419              5             12
Gi2/0/16         8491336         126321            758            560
Gi2/0/17             398              0              5              0
Gi2/0/18   4718303041417     3720361267              1            675
Gi2/0/19   2740295602976     2885078787              1            705
Gi2/0/20        10199901           9276              0            130
Gi2/0/21            1952             14              3              5

[Leo Laohoo]

1) Are the values accumulated over a standard interval?

Yes the values accumulate over time and do not "reset to zero".

2) Do the counters need to be RESET or CLEARED periodically?

I don't like this practice of regularly clearing out interface counters because interface counters play a significant role in troubleshooting line errors and other issues.

3) Is there a way for an interface utilization report to be produced on a recurring basis?

Yes, you can use SNMP to pull out details of the interface counters and use PERL scripting to format it the way you want.  If it's too much then you might look at third-party tools like, Solarwinds.