STP ethertype

Hi,

I don't see what is the ethertype for STP. Is it similar to the protocol identifier, which is 00-00 ?

Thanks for your opinion, best regards, Michelot

the standard you want is 802.1D - note there are lots of follow ons.

however - it doesnt use an Ethertype, but uses the "SAP and length" type ethernet format.

the IEEE put the standards online

formatting link

try a search on something like 802.1d spanning tree

Bonsoir Stephen,

Thanks for your words.

Yes, I found this. It seems it's a rare case where we have still the length instead of the EtherType.

And there is either the SNAP encapsulation, either the LLC no SNAP encapsulation.

Case 1 that I translated from a trace found on the web:

DA = 01-00-0C-CC-CC-CD, SA = 00-02-7D-71-B8-C1, Length = 00-40, LLC SNAP = AA-AA, CTRL = 03, OUI Cisco = 00-00-0C, PID PVST = 01-0B,

Case 2 (I extracted the tag):

DA = 01-80-C2-00-00-00, SA = 00-02-7D-71-B8-C1, Length = 00-40, LSAP =

42-42, CTRL = 03,

I knew the multicast DA of the case 2, but not the multicast DA of the cas 1. Do you know the difference?

Best regards, Michelot

Bonsoir,

It seems it is specific to the STP version of Cisco.

Best regards, Michelot