Because there could be long-resolved issues in play here, I'm a little curious why you are using firmware 6.42.03.0004 (Jan 2011) rather than performing a follow-up upgrade to something more contemporary such as 6.61.13.0006 (Nov 2014). See KB 14480 (
http://bit.ly/1rViaUk).
The next thing to check with such symptoms is whether there is noteworthy flowcontrol activity ('
code:show port flowcontrol
'). That in combination with the system uptime ('
') will provide an assessment of the flowcontrol rate over time. If Rx/ingress flowcontrol activity averages to more than one per minute on any port, then it is definitely worth treatment. The most common treatment is to disable flowcontrol on the whole switch/stack: '
code:set flowcontrol disable
'. (Upon issuing this command the link state of all affected ports will be briefly cycled down/up, but this tends to be transparent to attached (even PoE) users and applications.) Then assess the result - which should be an overall performance improvement.
If you have concerns about making such changes or flowcontrol does not appear to be a factor, then I suggest that you contact the GTAC (
http://www.extremenetworks.com/support/contact) to open a Support Case for more targeted assistance with the described problem. The C3-Series is a Lifetime Warranty product for the original owner.
Thank you.