question in switching for STP and loop

[Dr.X]

hi ,

i have a question in loop issue , will it occur in this case or not

i will describe my scenario as below :

now i have 4 switches connected with full mesh.

=================

3 of them has stp protocol enabled

only 1 of them is un manged and dont support STP protocol

====================================

the question is :

if i connected the 4 switches full mesh  , will  the loop occurs ??

as i believe , stp loop prevention depend on the switch itself not on their neighbour ,  but not sure from my understanding

wish to help

regards

[Joseph W. Doherty · Accepted solution]

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Posting

No, a loop won't form in the topology you've described.

[Dr.X]

great to hear that ,

can u explain ??

can i say a rule

"" if there is (n) number of switches  , we can say that (n-1) with STP and one switch without STP can deal to no loop  if there were connected with fulll mesh""

correct ?

[smitty6504]

Someone please correct me if i am wrong, but the unmanaged switch is nothing more then a smart repeater, so it is going to pass the BPDU from one switch right though the unmanaged switch to the other managed switch. The switch on one end will block the one port from the unmanaged switch as it will see a loop and do what STP should do and block the port(s).

There is no rule or formula you can really use to figure this out.

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

If there's only one or two non-STP switches, in a full mesh, you'll be okay.  Once you have at least three non-STP switches, in a full mesh, you have a loop between them.