# Spanning Tree Port States

**URL:** https://forum.networklessons.com/t/spanning-tree-port-states/1113
**Category:** Lessons Discussion
**Created:** [December 26, 2016, 11:01pm UTC](https://forum.networklessons.com/t/spanning-tree-port-states/1113 "2016-12-26T23:01:39Z")
**Posts on this page:** 1
**Showing post:** 29

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### Author: ![lagapidis](https://cdn-forum.networklessons.com/user_avatar/forum.networklessons.com/lagapidis/32/4949_2.png) [@lagapidis](https://forum.networklessons.com/u/lagapidis)
#### Post date: [January 2, 2023, 10:43am UTC](https://forum.networklessons.com/t/spanning-tree-port-states/1113/29 "2023-01-02T10:43:13Z")

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Hello Quirik

Switch ports in the blocking or alternate state **still receive BPDUs from the connected switch**. So for the following statement here is the explanation:

> [@lagapidis](#):
>
> SW3 will keep the information from the previously received BPDUs on Port B for 20 seconds which is the blocking timer

So before port C on SW2 went down, when STP was converged and stable, port B had received some BPDUs from SW2. These are the “previously received BPDUs.” When the topology changed, SW2 sent new BPDUs with new information, stating that it is the root bridge. SW3 does not process these yet, until the blocking timer expires.

What makes the superior? I assume you are referring to this statement:

> [@lagapidis](#):
>
> - Once this timer is expired, Port B will begin considering the BPDUs in the Listening state and will begin relaying SW1’s BPDUs to SW2 since they are superior

The statement says that once the blocking timer expires, the newly received BPDUs are considered. However, **they are not accepted because those received from SW1 are superior to those received from SW2.** So, SW1 becomes the root once again, as it should be.

Does that make sense?

I hope this has been helpful!

Laz

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