Quick question regarding mst

Is anyone working on, or have worked on a layer 2 network with MST with the root-bridge being
a switch outside the mst. I've been playing around with this getting stange results only to be told by afew of my ccie colleagues that the is a huge NO!! NO!! .Some Cisco docs i have mention it, describe how it should function, but in the end it doesnt work as they suggest.
Over the last few days i was considering putting mst up in number one place for difficulty in regards ccie, but with these new developments i.e. root bridge always being the IST master it have slipped down out of the top ten.
So just to be sure i'm not going to encounter this headache in the future, i'd like to hear if anyone has seen the setup in the field.

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Comments

rossonieri#1

never seriously tried that,
CST?

have you read this :
http://cisco.com/en/US/products/hw/switches/ps708/products_configuration_guide_chapter09186a0080518f21.html#wp1035423

it should be inside an MST region.

cheers.

EdTheLad

rossonieri#1 wrote:

never seriously tried that,
CST?

have you read this :
http://cisco.com/en/US/products/hw/switches/ps708/products_configuration_guide_chapter09186a0080518f21.html#wp1035423

it should be inside an MST region.

cheers.

That Doc doesn't say the root must be inside the mst, maybe you are confusing the IST master with the overall root bridge.

rossonieri#1

pls read the doc one more time.

no - you are correct that that doc didnt mention that a root bridge should stay inside an MST region,
but - it refers to our logical thinking how come that an MST region that we have created doesnt have a root bridge itself? can you? even a standard STP has it.

in your case maybe you have accidentally triggered a CST.

just my opinion.