errdisable_recovery.pdf explains why our HP-Blade suddenly has disabled port (turn red light from initial green) when connected to a switch.
This blade Catalyst 3020 ports must have been in
errdisable/error disable state. First, look for something like
1 2 3 4
#show interfaces gigabitethernet 4/1 status Port Name Status Vlan Duplex Speed Type Gi4/1 err-disabled 100 full 1000 1000BaseSX