BPDU's in STP

[chandra_rc16]

Can someone please let me know the type of BPDU's is STP and their funtion ?

I just know that there are three types of BPDU's 1.configuration 2.Topology change notification 3. topology change ack.

It will be helpful if i get more info on this or a link to that .

Thanks in advance.

Regards,

Chandu

[anand kumar]

Hi Chandra,

Here is the url/info regarding the STP & Bpdu's

http://www.routeralley.com/ra/docs/stp.pdf

Regards

Kumar

[chandra_rc16]

To which address the BPDU's are sent ?

Regards,

Chandu

[InayathUlla Sharieff]

Chandra,

Bridge Protocol Data Units (BPDUs) frames contain information regarding the Switch ID, originating switch port,MAC address, switch port priority, switch port cost etc.

Bridge Protocol Data Units (BPDUs) frames are sent out as multicast messages regularly at multicast destination MAC address 01:80:c2:00:00:00. When Bridge Protocol Data Units (BPDUs) are received, the Switch uses a mathematical formula called the Spanning Tree Algorithm (STA) to know when there is a Layer 2 Switch loop in network and determines which of the redundant ports needs to be shut down.

Three types of Bridge Protocol Data Units (BPDUs) are Configuration BPDU (CBPDU), Topology Change Notification (TCN) BPDU and Topology Change Notification Acknowledgment (TCA).

HTH

Regards

Inayath

[chandra_rc16]

Hi Inayath,

When a non-root switch is sending a TCN BPDU will it sent that to the multicast address or only to the root bridge through mac table ?

Regards,

Chandu

[rizwan shaikh]

Hi Chandra,

I will try answering your question, but  I have not tested in Lab.

Non-root bridge , will try to deliver TCN Bpdu to root-bridge using Root-Bridge's mac address  as all non-root-bridge switches would have mac address of Root-bridge-Switch in their mac-address-table already 

[Peter Paluch]

Hello Inayath,

Three types of Bridge Protocol Data Units (BPDUs) are Configuration BPDU  (CBPDU), Topology Change Notification (TCN) BPDU and Topology Change  Notification Acknowledgment (TCA).

Technically, there are only two types of BPDUs in 802.1D STP: the Configuration BPDU with the Type = 0x00, and the TCN BPDU with the Type = 0x80. What is called TCA is simply a regular Configuration BPDU, Type = 0x00, with the TCA flag set.

Best regards,

Peter

[chandra_rc16]

Do we have any link which described only about BPDU frames ?

All the fields and types .

[Peter Paluch · Accepted solution]

Hi Chandu,

The authoritative source of information is the IEEE standard.

http://ylescop.free.fr/mrim/protocoles/802/802.1D-1998.pdf

Check the Section 9 starting at page 128. Regarding the addressing of TCN BPDUs, they are also sent to the same multicast MAC address as configuration BPDUs.

Best regards,

Peter