Spanning Tree Protocol Tutorial

I am not sure if this has been posted before but this has helped me grasp the concept a little better. Just thought I'd share it:

http://www.cisco.com/warp/public/473/spanning_tree1.swf

Good day

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Comments

pamccabe

I second the link. I saw the link on the CCNA study group site awhile back. For whatever reason, STP has been a tough subject for me out of all the CCNA topics. This is a very good resource. Thanks for sharing.

havenlad

One question I have....if one end of a segment link is blocked, what is the point of the other end being forwarding, other than to notice the failure of the BPDU if the designated port goes down? Is that it's sole purpose - to send BPDUs?

pamccabe

havenlad wrote: »

One question I have....if one end of a segment link is blocked, what is the point of the other end being forwarding, other than to notice the failure of the BPDU if the designated port goes down? Is that it's sole purpose - to send BPDUs?

Yes, it only listens to and processes BPDUs. The point is if there is a topology change and it has to change its status. The network should be self-correcting. If it detects a failure at some point, it should detect it, correct itself, and continue processing packets. STP and redundancy goes hand-in-hand... at least that is how I understand it.

To clarify: blocking ports still listens to and processes BPDUs

iamme4eva

havenlad wrote: »

One question I have....if one end of a segment link is blocked, what is the point of the other end being forwarding, other than to notice the failure of the BPDU if the designated port goes down? Is that it's sole purpose - to send BPDUs?

What if the segment that was designated as the redundant path (so one end blocks and one end forwards) isn't actually a cable directly between two switches and has a hub in the middle?

There are still only two switches on the segment, so as far as the switches care it is just a link between two switches - but if you have user terminals coming in on that hub, they need a way on to the network. Because one end is forwarding, that end can still forward the user data for hub-connected terminals on to that segment - the blocking end won't, so loops will still be prevented.

Carnby

That was great. I tried leaving feedback, but there was an option to do so. The last slide said that I could leave feedback by clicking on the link in the top right. There wasn't a link.

Regardless, thank you for posting that. I'll be sure to watch it a few more times. ...Although I wish the animation took priority into consideration.

dsgm

Love this do they have anymore, helped me a lot with STP

havenlad

Excellent and simple explanation. I notice all over the internet the same thing is asked - this is the only place I have seen it answered. I now understand it - thanks

QuantumKnight

I am happy it was useful. I will keep trying to find more of these tutorials.