Wireshark · Wireshark-dev: [Wireshark-dev] Info on mst bpdu's

[Sake Blok <sake@xxxxxxxxxx>]

Hi,

Yesterday I was troubleshooting a spanning-tree issue at a customer.
The customer is running MST and I collected some BPDU's. Unfortunately
these BPDU's are not properly decoded by Wireshark. In order to start
writing my first (real) addition to Wireshark I downloaded the
IEEE 802.1D-2004 and the IEEE 802.1Q-2003 and read though them (I added
a link to IEEE 802.1Q-2003 to the Wiki page on STP).

To me it looks like the BPDU-packet layout described in that document
is not the one I am seeing in my tracefile. First of all the 
Configuration Identifier field (octet 39 of the BPDU) is not 0 as
the IEEE document states, but seems to be the length of the MST extension
data in de BPDU. Also the Extension data is formatted differently from the
specs.

Does anyone know if the Cisco-implementation of MST is proprietary? Or is
there maybe a standard that evolved after 2003? Any documentation on
(cisco) MST BPDU's is welcome. Also if someone has some STP, RST and MST
packets laying around in traces, please send them to me so when I write 
a patch I can make sure I don't break things for other BPDU's :)

Cheers,

Sake