PVST Calculation

[vishalpatil86]

Dear All,

How PVST works?

can anyone explain woth the help of an example?

Thanks,

Vishal                  

[milan.kulik]

Hi,

you admitted VLAN99 is discontinoue in your LAN.

Where is the discontinuity point?

Let's assume VLAN99 is not configured on the trunk between yoiur switch 221 and the core switch 4506.

In that case, swicth 221 will not receoive BPDUs for VLAN99 from the core switch and voice versa.

So one of the switches within the sw221 ... sw226 chain will become STP root for VLAN99 in this part of VLAN99. (it's sw223 in your case.)

And one switch (4506 in your case) will become a root for the second continous part of VLAN99.

Is it clear now?

HTH,

Milan

[milan.kulik · Accepted solution]

Hi,

acually, each switch believes to be an STP root until it receives a BPDU with better priority than its own one within the VLAN.

Is it clear now?

HTH,

Milan

[vishalpatil86]

Thanks Milan, understood clearly