STP prioritize port priority over System-Mac-Address in my project.

[eitanbenari4]

Root bridge is IOU1

i executed this script on the kali machine. after it the egress port to the root transitioned to the alternative state, despite the lower mac address of the Root-bridge. CHAT said its becuase of a lower port priority, but from what i know, port priority only comes after mac address.

[eitanbenari4]

Well I did a little check. In stp only the root send config bpdu and changes the fields of bridge/root mac. But in rstp every sw sends config bpdu, which explains why the Mac address needs to be identical to the bridge id(the sw the made the bpdu)

[MHM Cisco World]

Again your topolgy since there is no loop in connection (triangle or rectangle) there is no BLK.

For MAC let me summary mac 

Bpdu source :- mac address of SW 

Bpdu destiantion:- multicast of STP (this mac is different between stp modes)

Bridge -id :- is the mac of SW from where this bpdu come from 

Root -id:- this mac address of root SW

MHM

[eitanbenari4]

In a case of indirectional link failure, the switch can block a port even if there are no loops. Check out backbonefast

[MHM Cisco World]

Friend check out what ?

backbone fast is feature of STP which use to stop loop 

your topology is chain of SW there is no loop

anyway 

let other help you I am little busy sorry 

goodluck 

MHM