Why the port is blocked, it will be the root port !!?

[Fotit]

Hello

please,look at the the capture joined, it's about ports roles election

All settings are defaults, i just build the lab with differents links, to have differents cost values

My probleme is about RP of switch (1)

in my analyse, the port f0/4 switch (1) is the root port, because the priority port F0/1 sender in swicth (3) witch is the root, is 128.1

so it win, and then f0/4 switch (1) will the RP

But packet tracer make it in blocking state !! or just a bug in link lights !!?

I need to know what happen in this topology? and why this port isn't RP?

thinks

[Seb Rupik]

Hi there,

The final STP tie-breaker will choose the port connected to the lowest port number on the remote switch.

In your case both (SW1)fa0/3 and (SW1)fa0/4 connect to the root-bridge(SW3), but (SW1)fa0/4 is connected to the remote port (SW3)fa0/1 whereas (SW1)fa0/3 is connected to the higher remote port (SW3)fa0/2.

(SW1)fa0/4 will therefore be selected as the RP.

cheers,

Seb.

[Fotit]

Seb Rubic

You don't understand my problem

My question isn't how to to elect RP

in this case, Before looking to lowest port number, you verify the lowest port priority !!

I know by root port election logic, that f0/4 (SW1) will be the root port

the show st command confirme that, but links lights not !!

I think there's probleme in packet tracer or i will verify my ports connextions on SW1

[Seb Rupik]

With PT when you encounter something which defies standards or even logic then it is probably a bug. Unless you are having to use PT for further education courses, you should switch to an emulator such as eve-ng, cml2 or gns3.

Can you share your PT file so we can take a look?

cheers,

Seb.

[Martin L]

Do not follow PT light (green /orange); Use CLI outputs.  I noticed those light can misbehave in PT especially when u have 2 links between switches and they are not in port channel. Or when you have multiple STP instances (1per 1vlan). 

IF u do not use 2 links between switches, those PT lights are correct and follow show spanning tree, right?

you can attach PT file here but it must be in a zip format. we check check if it is a bug or not. I can send a bug report to PT.

what is your OS ? what is PT version?

Regards, ML
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