We need some help in determining the cause of a network outage. We have two 6509 switches at our core layer, 3550-12G switches at our distribution layer and 2950XL switches at our access layer. Everything was working fine for months, no major changes to the network. On Monday, we lost network connectivity to many of our 2950 switches and some of our 3550 switches. We found that many of the gbic gigabit ethernet ports were either in disabled state or err-disabled state. Syslog messages showed no apparent problem with the exception of a duplex mismatch on two separate access layer switch ports (apparently a user plugged a hub into two different switch ports). Would this cause a network wide outage? Why would gigabit ethernet ports shutdown across the network?
