Cisco MST question: Blocking vlan on trunk port

If I block a vlan on a trunk port and the vlan is part of an mst instance, will the entire instance be blocked or just the specific vlan?
dsterlingAsked:
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

x
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Don JohnstonInstructorCommented:
If I block a vlan on a trunk port...
How are you going to block the port?  

Or do you mean that the port gets blocked by spanning tree?

If the latter, then the instance is what does the blocking.  And all VLANs in that instance will be blocked on that port.
dsterlingAuthor Commented:
Don,

Thank you for your comment, I should of explained more.

I would not allow vlan 8 on the trunk port. Vlan 8 is part of an MST instance that has a few other vlans,  so will not allowing vlan 8 on the trunk port block the entire instance that vlan 8 belongs too?

Thank you
Don JohnstonInstructorCommented:
Okay. Gotcha.

In that case, the previous answer stands.  Not allowing a VLAN over a trunk will not affect the other VLANs in the same instance.  In MST, the instance is blocked/forwarded for a port.  All the VLANs in the instance then behave accordingly.  

Now here's the catch: Let's say there are two paths (path A and path B) for the instance which VLAN 8 is assigned to. And you remove VLAN 8 from the trunk link that makes up path A.  But MST is blocking path B, then VLAN 8 will not be able to get through.

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Switches / Hubs

From novice to tech pro — start learning today.