BPDU Matrix

I have read about BPDU features, when configuring  Access Port, Port-Fast, Loop Guard , BPDU Guard, UDLD, BPDU Filter, and you name it. It is very confusing..

Sometimes you use one feature and sometimes you combine 2 or even 3 features together. Sometimes they are configured by Port and sometimes Globally.
I would like to know  if there is a Matrix that clarifies the combination of those features in order to get a good picture?

I mean a Table with Columns and Rows that shows what does one feature do when configured by itself and when it is combined by other feature(s), when it is configured at Global level and when it is configured at port level.

Cisco should have thought about creating this table if they have not done so.

Any help will be very much appreciated.

Thank you
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Don JohnstonInstructorCommented:
I don't think such a table exists.

BPDU Guard and BPDU filter require portfast to be enabled. There is a globally configured default feature for them which enables them on any port that has portfast configured.

UDLD and loopguard are standalone protocols primarily used to detect unidirectional links. IIRC, enabling UDLD globally will only enable it on fiber links.  For copper links it must be enabled per interface.
jskfanAuthor Commented:
Ok...If we configure all Non-Uplink ports as Access ports. Then inadvertently someone will plug a switch or Blade or ESX host that has Network Adapters that negotiate the Trunk, will this be able to create Loop or topology change, or Access port makes it safe ?
Don JohnstonInstructorCommented:
Access port vs. trunk port doesn't have any affect on whether a loop can occur.
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jskfanAuthor Commented:
I mean if a switch port is configured as access port, but you plug a switch into it ...will this create Loop or topology change ?
Don JohnstonInstructorCommented:
It is going to depend on whether adding this switch creates a loop.  

So the simple answer is:

If the new switch only has a single connection to the existing network, in other words, no redundant links (no loops), then no.  There is no topology change.

But if the new switch has multiple links to the existing network, then you've got loops.  And you have a topology change.

Now there's a more complicated answer but I think it best to defer that for another time. ;-)
If the new switch only has a single connection to the existing network, in other words, no redundant links (no loops), then no.  There is no topology change.
True, but when you attach device to port, and port status change TCN will be sent anyway if portfast is not set on that port. I guess that goes to more complicated answer part. :)
@jskfan For topology change read this article and read this for loop example.
There is a picture of simple loop. :)
Looks like you don't understand what loop is.
If you just attach switch to access port that don't create loop. You need to have way back to the same switch on some other port in the same network. In the case where STP is not blocking one link you have network frames that live forever.

And there is also this animation on the first link , don't miss it. :)
Refer to the Spanning Tree Flash animation to see an example that explains how the Spanning Tree initially converges. The example also explains why a blocked port goes into the forwarding mode because of an excessive loss of BPDUs, resulting in STA failure.

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jskfanAuthor Commented:
I will check that later.
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