Help, a problem with STP

[tuongql01]

SW2#sh int tru

Port Mode Encapsulation Status Native vlan

Fa0/1 on 802.1q trunking 1

Fa0/2 on 802.1q trunking 1

Fa0/3 on 802.1q trunking 1

Port Vlans allowed on trunk

Fa0/1 1-1005

Fa0/2 1-1005

Fa0/3 1-1005

Port Vlans allowed and active in management domain

Fa0/1 1

Fa0/2 1

Fa0/3 1

Port Vlans in spanning tree forwarding state and not pruned

Fa0/1 1

Fa0/2 none                       -> The cause anh how to fix error ?????

Fa0/3 1

[Rolf Fischer]

Hello,

Port Vlans in spanning tree forwarding state and not pruned
Fa0/2 none                       -> The cause anh how to fix error ?????

VLAN 1 will never be pruned by VTP and we can see it is active, so apparently port Fa0/2 is not in spanning-tree forwarding state.

What does 'show spanning-tree interface fa0/2' say?

HTH
Rolf

[tuongql01]

Dear Rolf Fischer! 

SW2#sh spanning-tree int fa0/2

Vlan Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

VLAN0001 Altn BLK 19 128.2 P2p

[Rolf Fischer]

Ok, so port Fa0/2 is an Alternate Port (to the root bridge) and the spanning-tree protocol has set it to Blocking state in order to avoid a layer-2 loop. We don't know the topology and STP configuration but it looks like expected behavior. Do you have any problems with the device connected to that port?

Regards,
Rolf