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Revision 10 as of 2007-05-05 01:06:14
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Editor: ClintonWork
Comment: Add note on Cisco PVST+ STP BPDUs
Revision 11 as of 2008-04-09 13:42:59
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Editor: tlvmail1
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XXX - Add a simple example capture file to the SampleCaptures page and link from here. Keep it short, it's also a good idea to gzip it to make it even smaller, as Wireshark can open gzipped files automatically. * attachment:SampleCaptures/stp.pcap

Spanning Tree Protocol (STP)

XXX - add a brief STP description here


XXX - add a brief description of STP history

Protocol dependencies

  • ["LLC"]: Typically, STP uses [:LLC:802.2 LLC] as its transport protocol, running on link-layer protocols in the LanProtocolFamily such as ["Ethernet"].

Example traffic

XXX - Add example traffic here (as plain text or Wireshark screenshot).


The STP dissector is fully functional and supports IEEE 802.1D BPDU, Rapid Spanning-Tree BPDUs, and MST/MSTI BPDUs. Also add info of additional Wireshark features where appropriate, like special statistics of this protocol.

Cisco has a custom TLV extension called Per Vlan Spanning Tree (PVST+). The extension is added to 802.1D and RST BPDUs sent on 802.1Q VLAN trunks. The extension at the end of the BPDU advertises the VLAN ID (PVID) that the BPDU was sent on. The extension has the following format. It should be noted that only 802.1D and not RST BPDUs include the one padding byte for alignment.

  • Even byte padding (802.1D only): 1 byte
  • Type (only PVID type 0x00 is supported): 2 bytes
  • Length: 2 bytes
  • Data: PVID is 2 bytes

Preference Settings

There are no STP specific preference settings.

Example capture file

* attachment:SampleCaptures/stp.pcap

Display Filter

A complete list of STP display filter fields can be found in the [ display filter reference]

  • Show only the STP based traffic:

Capture Filter

  • Capture only the STP based traffic:


STP (last edited 2011-06-27 05:32:14 by WenchaoWang)