Network congestion in Catalyst switch

[13jobsp90]

How to check the output or if there are any network congestion or overload traffic in catalyst switch in model 2960?Briefly explain 

[Joseph W. Doherty]

Interface drops and/or queue depths may be such indicators, but what's your definitions of congestion and/or overload?  The reason I ask, I consider an interface congested whenever a packet cannot be immediately transmitted.  Many possible definitions for overload, one, perhaps being oversubscribed.

If you dealing with a perceived performance issue, it's very easy to incorrectly analyze such based on congestion and/or overload.  What you want to analyze is service requirements and whether they are being met.

[13jobsp90]

I have a pbx software installed in workstations. So I was told by the PBX vendor that PBX software is having lag issue due to the network congestion from the network not from the IPPBX application. So How do I check that in the switch? like sh interfaces summary etc, like so many terms like input queue, output queue etc.? Can anyone explain with the sample output & its each ouput terms?

[Joseph W. Doherty]

Actually, that can be difficult to verify using just "stock" switch stats.

VoIP has comparatively demanding service requirements.  VoIP is often the "poster child" for the need for QoS.

If you're not using QoS to support your PBX traffic, would recommend you focus your efforts there rather trying to further analyze your switches.

[Leo Laohoo]

Check for Traffic Output Drops and Overruns.