Spanning Tree not working properly when backup port is connected

[nicolasmonta1807]

I currently have a working network that uses inter-vlans and a dhcp server as showed here

Everything works as expected that way and the PC's are able to retrieve their IP's according to their vlans.

The problem is that i've been trying to configure Spanning Tree to add redundant connections between each floor's switch and the central one labeled as "NORTE" which is the root for all vlans in order to allow connection to other routers and the datacenter but as soon as i add those redundant connections it seems to be a looping or something else between the PC's, because when i start them it gives a weird ip retrieved or relayed from its own MAC but then there is no IP at all, for example:

I really don't know why this is happening, since the Switches show the root port properly and the backups are shown as Alternative but Blocked, which i believe should be that way. Other weird fact is that if the backup port is connected and the direct root one is not, it also works properly.

[MHM Cisco World]

Stp must stop loop'

Can you sure that all SW share same stp mode?

[Flavio Miranda]

Hello,

  You might consider that this is a simulator and the problem can be related to this fact and not network behavior. But, if you are facing any issue related to STP you must be able to see it on the switches logs or debug.

  I´d like to add a comment and hopefully you dont take me wrong but usually we dont build network redundancy by interconnect access switch like this. A much more realistic way to build redundancy would be you add another "NORTE", it could be NORTE2, and then connect each Access switch to both.  But this is just a side notes.