RPVST issue

[Dennisvw]

Hi,

I'm in the middle of changing the uplink for several switches connected to a central 5412zl switch and experiencing something strange related to RPVST.
All switches are configured with RPVST and the 5412zl is root for all of the involved vlan's.

From the 5412zl I have an Procurve 2920 (SW1) connected which again connects to an Procurve 2920(SW2).
Now when connecting the 5412zl to SW2 i expect the connection between SW1 and SW2 to go in to Blocking and the connection between 5412 and SW2 to go into Forwarding mode.
The opposite happens:
The interface connecting the 5412 and SW2 goes into blocking on the root switch (5412zl); is that possible at all? thought that the root switch always will be in Forwarding?
Now, when taking a different interface on the 5412zl and connecting that to the same port on the SW2, it works as expected.

Both interfaces on the 5412zl are configured exactly the same, the only config on the ports is: "tagged vlan 2,3-4,7,10"

How to proceed in solving this mistery?

Kind regards,

Dennis

Edit: One thing I forgot is, when configuring a single port trunk (trunk b18 trk5) on the port that caused the issue it works as expected.
But this could never be a requirement, because the ports that doesnt show this issue aer also just normal ports with the tagged vlans

[drk787]

Hi 

Do you still have the issue.

Can you share the 'show spanning-tree' output from the three switches.