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New Member

BPDU's in STP

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

Regards, Chandu
  • LAN Switching and Routing
1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

BPDU's in STP

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

8 REPLIES
New Member

BPDU's in STP

Hi Chandra,

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

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

Regards

Kumar

New Member

BPDU's in STP

To which address the BPDU's are sent ?

Regards,

Chandu

Regards, Chandu
Cisco Employee

BPDU's in STP

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

New Member

BPDU's in STP

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

Regards, Chandu
New Member

Hi Chandra, I will try

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 

Cisco Employee

BPDU's in STP

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

New Member

BPDU's in STP

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

All the fields and types .

Regards, Chandu
Cisco Employee

BPDU's in STP

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

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