CCNP Lab - PVST configuration and verification question

Hello,

I've got a lab which diagram is the following:

I have 3 different Vlans (10, 20, 30) and I need to create an PVST instance for each of them.

The "trees" I need to build are as followed:

I don't really know how to approach it, have and tips?

diagram.jpg

PVST.jpg

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Comments

networker050184

Do you know the criteria for electing a root bridge? Do you know the criteria for switches to select their path back to the root bridge?

Look into these and go from there.

guycho

Yes, I know the criteria.
I guess that the first think I will do is to configure the root bridge for each vlan as shown in the picture.
I looked up for the command and it looks pretty easy.
The creteria is by link cost which is measured by the link bandwith?

networker050184

Sounds like you are on the right path. Once you know how the elections occur then the easy part is finding the commands to influence them as you see fit. Good luck!

guycho

So the election proccess is the only thing I should know to acomplish the PVST instance creation according to each VLAN demand?

networker050184

You should know how the root bridge is elected and how each of the non-root bridges choose their path to the root.

MrBrian

networker050184 wrote: »

You should know how the root bridge is elected and how each of the non-root bridges choose their path to the root.

Yea that's pretty much all you need to figure out. Just find out how to configure the root bridge.. and then how each device going away from the root will decide what ports to keep active. I.e. each switch will pick one Root port, and then decide on all other segments if it should keep the link in forwarding, or block it. Just research "spanning-tree decision process" or "spanning-tree election process," and you'll find plenty of info.

Once you understand the way it works, try and mark your topologies before you start configuring it, so you know what you're expecting to happen.. and it will be easier for you to simply reference your topology to remember how you want it to flow(at least for me).

I think the tricky thing about spanning-tree isn't necessarily the election process, but the fact that there's a different instance per vlan.. coupled with the spanning-tree show command output being fairly confusing if you're not used to seeing it. You'll get it though