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dbuckley77
Beginner

Orange lights on ports on 3750G

We have a pair of 3750Gs that we are seeing some orange lights on.  There is a trunk between the two switches and off of each port a loop hangs, ie port 5 on the first switch is connected to a bunch of other switches that eventually come back to port 5 on switch 2.  We have three ports lit orange on switch 2 and I have checked the speed/duplex settings.  They are the same on the Cisco 3750G as they are on the non Cisco switches that the orange ports are connected to.  Everything is running at 1g/full.

The ports are setup as access ports and we are running pvst.  I noticed all of the orange ports are showing as stp blocking ports.  Is this why I am seeing the ports as orange and is that normal and acceptable?  There are no network performance issues.

2 REPLIES 2
balaji.bandi
VIP Master

As you mentioned Organge or Amber ( Amber :Port is blocked by Spanning Tree Protocol (STP) and is not forwarding data).

 

This is nature of STP, you need to Draw a Diagram and see where this Loops are, if possible correct it, but this is what your intention of network design, Make Ports in Priority of STP, so you will see less interuption in the network.

 

STP troubleshoot :

 

https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/28943-170.html

 

 

BB

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Giuseppe Larosa
Hall of Fame Master

Hello @dbuckley77 ,

you see STP in action in your network, the STP blocked ports are not designated in theri segment meaning that there is someone seiding a better STP BPDU   ( lower cost to the root bridge or lower sender Bridge ID).

STP is designed to prevent bridging loiops and it does its job by blocking redundant ports.

To be noted on access ports Cisco switches senf out IEEE standard BPDUs that can be understood by non Cisco switches if running STP.

 

I would say it it normal anc acceptable what you see.

if the ports would be forwarding on both sides you would have a  root bridge located in the non Cisco switches and the trunk between the two C370 woulld be blocking on one side for the affected VLAN.

 

You can check with

show spanning-tree vlan X detail

 

who is the root bridge for the VLAN X,  what C3750 is more near the root bridge and the blocking ports should be on the other device ( or also on the nearest switch in that case the port with the lowest interface ID wins and it is the designated port for the segment all the others will be blocked)

 

Hope to help

Giuseppe