spanning-tree portfast on M8024-k

Hi guys,

I have 2x M8024-K blade modules (Fabric A1 and A2) stacked together using ports 19 & 20 in each switch.

My issue is that when I issue the "spanning-tree portfast" command to any of the tengig interfaces, the command is accepted by the CLI (it doesn't report any errors) however when I do a "show run", the command is not listed anywhere in the running-config... and not reflected under the interface where I'd expect to see it.

I've recently deleted the startup-config and rebooted back to a factory default config (except for the enabled stacking, disabled simple mode and enabled enable password)...

***** I type this......

console(config)#interface tengigabitethernet 1/0/1
console(config-if-Te1/0/1)#spanning-tree portfast
console(config-if-Te1/0/1)#end
console#show run

***** and get this....... NOTE: command is not reflected in running config.

!Current Configuration:
!System Description "PowerConnect M8024-k, 4.2.1.3, VxWorks 6.6"
!System Software Version 4.2.1.3
!Cut-through mode is configured as disabled
!System Operational Mode "Normal"
!
configure
no mode simple
vlan database
vlan routing 1 1
exit
slot 1/0 2    ! PCM8024-k
slot 2/0 2    ! PCM8024-k
stack
member 1 1    ! PCM8024-k
member 2 1    ! PCM8024-k
exit
interface vlan 1
exit
username "root" password e6e66b8981c1030d5650da159e79539a privilege 15 encrypted
enable password 7a7e91247f2a1267d68cb6aef6d2ebb9 encrypted
exit

What am I missing ?