STP blocked trunk ports still green

[Marko Farkas]

Hi all!

Here's the deal: I just bought 3 2950-24 switches for my CCNP pursuit and found something strange with the LED ports and STP configuration... All 3 switches have only 1 vlan (the default vlan 1), they are connected to each other with trunk ports (dot1q) and one of the switches is the root bridge of course. One of the switches has it's port blocked as it should have, all in all everything is working as it's supposed to be... Now, I always thought that the blocked port would change his LED color to amber on the switch but all of my ports (trunk ports) are green, including the blocked one, is this normal? I've searched the forum and found similar questions from people and some answers said that this is normal and some that it's not.... When I change the ports to access mode the port that should be blocked does indeed turn to amber... note that there are no other vlan's configured and the only ports on the switches that are connected are the trunk ports... Can anyone help with this issue?

Cheers,

Marko

[andtoth]

Hi Marko,

I did research regarding this and I can tell you that this is an expected behavior.

When an access port is in STP blocking state, the port LED is amber.

When a trunk port is in STP blocking mode, the port LED is green.

Your switch is working as designed and this has been confirmed by our developers.

Best regards,

Andras

[Marko Farkas]

Hi Andras,

thanks for the reply!

Your reply is like my STP...rapid!

So this is normal behaviour on all cisco switches?

It's funny that Cisco materials and manuals state that the ports in blocking state will become amber, I guess they just don't state what type of ports does that refer to... As I am drawn more and more in the Cisco world I found that a lot of things they state are realy ambiguous, so much for the precise science of 0 and 1's

Cheers and thanks,

Marko

[andtoth · Accepted solution]

In my understanding this is the same behavior across all Cisco Catalyst switches. The materials probably don't emphasize that only access port leds will turn amber because trunk ports usually carry more than one vlan and since we have per-vlan STP we might not block all vlans on a trunk port. I understand you are only using one vlan on your switch and trunk port but looks like the implementation does not consider the number of blocked vs active vlans, it just displays a green led if it's a trunk port.

[Marko Farkas]

Yea, I guess that was their way of implementing the feature... I configured it this way so I could rule out all of the possibilities of other vlans enabling that port to be in a forward state, thus making it go green... At least I'm releafed I didn't buy faulty gear

Anways thanks for the reply!

Cheers,

Marko