Spanning tree issue

[dbuckley77]

I am experiencing an issue where when I plug in a port which is set as an access port to vlan XXX it becomes the root port for another vlan on the switch vlan 9.  I have posted the config below.  to be very specific gi1/0/6 is access vlan XXX and gi1/0/11 is access vlan 9 (management for the switch).  With gi1/011 plugged in it is the root port for vlan 9.  When I plug i n gi1/0/6 it becomes the root port for vlan 9 even though it's not a member of vlan 9.  We are running pvst. 

config

[Francesco Molino]

Hi

Right now, gi1/0/11is the STP root? For all vlans or just vlan 9?
As per the description of this port, it seems normal because you should have a core switch connected?

Is this switch the core switch?
You need to manage the priority stp for each vlans on each switches. If not set then the default 32768 value gonna be the priority.
If you want this switch to stay root STP for this vlan, you need to configure it using stp priority commands as you did use for other vlans.

On all ports facing clients (trunk or access as soon as it's a client port), you can configure the spanning-tree root guard to make sure the device that'll be connected to that port will never become root STP.
They're also other commands that you can implement to control your STP like bpdufilter and bpduguard

What are connecting to port Gig1/0/9?
Is it a switch?

[dbuckley77]

gi1/0/11 is only the root port for vlan 9,  not the other vlans

This is not a core switch.  The core switch is what's on the other end of gi1/0/11.

gi1/0/9 is connected to another switch.

[Francesco Molino]

The core switch is the one connected to g1/0/11. This is what I bet when reading the description.

How the STP is configured there?

Is it normal that this switch is root for some vlans?

On port g1/0/9, have you applied the STP config root guard and/or bpdufilter?

Not bpduguard as it will block the port as soon as it receives BPDU. Root guard will also block the port is the received priority is higher than the actual switch.

You have to configure your priority on this switch to ensure no one is gonna be the root. What priority is set on the new switch you're trying to connect?

[dbuckley77]

int gi1/0/9 is not an issue, int gi1/0/6 is .   when gi1/0/6 is plugged in it takes over the role of root port for vlan 9 which was previously int gi1/0/11

pvstp is setup

[Francesco Molino]

So sorry, Yes same questions apply for g1/0/6. What's connected to it? how it is setup? ... Same questions as previous post

[chrihussey]

There is a good chance that g1/0/6 is coming up as a trunk port which is causing the issue. Try adding "switchport mode access" to the interface configuration and make sure the connecting device will not also try to negotiate as a trunk.

Also, if it is indeed connecting to another switch, make sure you don't have a loop in the network.

Hope this helps

[johnd2310]

Hi,

Your ports are probably in trunk mode. If you need to configure access ports, you need to explicitly  specify "switchport mode access" on all access ports.

what is the output of the following command on gi1/0/6:

"show interfaces gi1/0/6 switchport"

look for the "Administrative Mode: and Operational Mode:" 

Thanks

John