1920 JG924A - RSTP Root Port has incorrect Root Switch

[FryFubar]

Hi,

We have a network that look a little like this:

                        E ----> F                                   

                        |

A ----> B ----> C ----> D

                         |

                         G                                                   

We've got RSTP enable across all switches, and for the large part, it's working as expected. The problem seems to be with Switch D in this example.

All the other switches in the diagram have switch A as the root, which is good, but switch D has elected switch C as it's root. On the root port of switch D, the Designated Bridge is indeed switch C. 

To be clear,  AFAIK, the config works for all the other switches, e.g the root of switch F is switch A.

Has anyone seen this behaviour? Is there a setting in the config I'm missing? It feels like BPDU is being dropped somewhere.....

Any help would be greatly appreciated, I've been scratching my head for the last couple of days.

[drk787]

Hi,

Can you share the configurations of these switches. Are all these of same model (HPE 1920)?