Switch topolgy change and Loops

In our environment they have 2 sites..Main site and Fail over Site.
A Vendor , incidentally or accidentaly, brought a blade and plugged it into a switch, and created topology change or loop (I am not sure which one), the main site failed over however since the VMware environment was not properly set up for failover since they have affinity rules set up,most of the VMs did not failover..

I would like to know what could have been done on the switch to prevent this catastrophe  in the future.
I have asked questions in the past, and some experts said , it is better practice to configure unused switch ports as access ports, I have done some reading and some articles say even if a switch port is in access mode, it will still send or receive BPDUs, which means it can cause topology change or loop.
Any idea ?

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Data center switch ports that are not in use should be set to shut down or disabled, so that vendors or inexperienced employees cannot connect devices and cause problems.  Keeping unused ports disabled will force people to contact you and then you can plan how the port should be configured before enabling it.  It is not clear how the vendor brought down the network, I would assume that the physical switch port was not configured for the Vswitch running on the VMware server and that somehow caused the issue.
Don JohnstonInstructorCommented:
A spanning tree topology change (by itself) will not cause an outage.  A topology change caused by a new redundant link (a loop) may cause a temporary interruption in traffic flow.

Without know a bit more about this scenario, it's impossible to say what can be done to prevent it since we don't know exactly what caused it.

A vendor inserted a new blade into a switch and caused a topology change???

What kind of blade in what kind of switch?  I can't see how just inserting a linecard into a switch chassis would cause any traffic interruption until cables get connected to ports.  

Or are you talking about a blade in a server chassis?
jskfanAuthor Commented:
I believe Server Blades have an internal switch .
VMware ESX I believe has also an internal switch though I guess it is virtual switch.
However I agree, if you bring one new switch and connect it to a switch port on a switch that is in production , it should not create a problem, since the new switch does not have another connection to another network.
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jskfanAuthor Commented:
<<Or are you talking about a blade in a server chassis>>>

Don JohnstonInstructorCommented:
I suspect there's more to this than just adding a blade to a server chassis.

If there's a virtual switch and it's incorrectly configured, then there would be an existing problem where adding a blade wouldn't cause a new problem.

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jskfanAuthor Commented:
Thank you
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