Understanding Spanning-Tree Port-Priority

In this video we will learn about the spanning-tree protocol port priority. We will examine the spanning-tree root bridge election process, root port and designated port election process and talk about how port-priority relates to these various elections.

We will look at an example on real Cisco gear and show you how to manipulate port-priority in such a way that will help you understand it's purpose thoroughly

[johnhobbs]

Almost 9 years ago to the day and your videos continue to help others? Great job! I had a student stuck and I couldn't get him out. But I found this video and your explanation did the trick! Thank you! John

[midoahmed]

Now I understood the root port election, Thank you very much.

[umarali]

I was looking for this information since last couple of days. Excellent explanation.

[essayasomichael]

Simply understandable way of explanation. You solved my problem. Thanks.

[ando]

Thanks for this video. Explained simply and understood

[astorinonetworks]

@fumega You can do that to enable a type of load-balancing but you are not adding more bandwidth per vlan. You still have 1 interface forwarding and 1 interface blocking per VLAN.

If I leave the defaults I have Fa0/23 forwarding and Fa0/24 blocking for both VLANs. If we change the port-priority of Fa0/24 of Cat1 for only VLAN 2 you would have Fa0/23 forwarding for VLAN 1 and blocking for VLAN2 and Fa0/24 blocking for VLAN1 and forwarding for VLAN2 on Cat2

[pahee]

Well explained. Great video. Thank you!

[jide]

This topic is well explain in the easies way possible, many thanks - I have subscribe for all your post

[avtarasinghsaini]

Perfect explanation ! it's help me a

[amitkoolmar]

Awesome simple clear explanation. Thank you!

[koudry]

Thanks, very simple and clear to the point.

[muhammadyaqoob]

Really good explanation! Thanks for uploading :)

[fumega]

@astorinonetworks
1Hi Astorino.
First thank you for you fast reply.
When I said that we would have more bandwidth per Vlan, I was referring to the fact that with the default STP port Fa0/24 on CAT2 would be blocked for all Vlans, and Fa0/23 would be the forwarding for all vlans (root). So if we changed the priority for Vlan, let's say, 6, on Fa0/24 of CAT2, Fa0/24 would become the root of CAT2, and Fa0/23 would be ALTN blocked for Vlan6. So we would have the Fa0/24 only for Vlan6 and Fa0/23

[wagnerj]

Very good explanation.  Much thanks.  It has been a long time since I needed to do this and the refresher is great.  I am actually using Brocade switches, but spanning-tree is spanning-tree.

[fumega]

(2)
unchanged, than we would have the Fa0/24 of Cat2 being the root for Vlan 2 and Fa0/23 being the root for Vlan 1 right? This design would allow more bandwidth per Vlan.

[xaxaxa]

Very good explanation, i was stuck for an hour trying to find why changing local port priority doesn't affect how a switch choose designating port on my topology

[fumega]

(1) Hello.

I've just discovered your website and Youtube videos, they're amazing!

By the way, we can take advantage of this feature in order to increase the available bandwidth per Vlan right? For instance, if there were two vlans, 1 and 2, by default all switches would have the same forwarding and blocking ports for all vlans. But if we changed the port-priority of VLan 2 on Fa0/24 of CAT 1 to, let's say, 32 (spanning-tree vlan 5 port-priority 32) and left the vlan 1 port priority

[PowerUsr]

Great video and thank you. I figured you can load balance by just switching which vlan you want the root bridge to operate on. I suppose this is easier. Do you think changing port priority is simpler and cleaner when controlling or load balancing your Layer 2 architecture?

[vishalcv]

It was really 🔮 clear thank you so much.

[fumega]

@astorinonetworks
2 only for vlan 1. So every Vlan would have its own 1Gb/s port vs 1Gb/s shared port.
I don't know if this works in production, that why I'm asking ;-)
Regards.