Answer / jitu

Yes, this really is the case. However, I do think there is
some confusion as to what happens to a Portfast enabled port
when it receives a BPDU. Upon receipt of a BPDU on a
Portfast enabled port, the port will immediately loose its
PortFast feature. This does not mean that the port will
show Portfast disabled in the "show spanning-tree summary"
output. Rather it means it will act as a normal STP port
and transistion through the STP states and will eventually
end up in either a blocking state or a forwarding state.



If the BPDUs that were arriving on the port were
"non-superior" BPDUs, the port would transistion to the
blocking state. Once these BPDUs stop the port would
recover and again participate in Portfast.



If the BPDUs that were arriving on the port were "superior"
BPDUs (means a lower bridge priority), then the port would
transistion to the forwarding state. This can cause a
permanent STP recalculation throughout your switch network.



Enabling BPDU Guard in addition to Portfast will prevent
bridging loops and/or topology changes from happening,
because upon receipt of BPDUs (superior or not), the BPDU
Guard feature immediately err-disables the port and must
manually be reenabled.

Right Mr... sahin ( hehhehe)

Answer / parshant jaswal

HI SHAHIN
1. WHEN YOU ARE ENABLING SPANNING TREE PORTFAST ON ANY
INTERFACE THAT MEAN YOU ARE KILL SPANNING TREE ON THE PORT.
PORT NEVER TAKE PARTICIPATES ON THE ELACTION OF ROOT BRIDGE.
2. AND PORTFAST FEATURE BYPASS THE LISTENING, LEARNING
AND MAX AGE
3. YOU CAN ENABLE BPDU GUARD FEATURE ON ALL NON-TRUNKING
FOR TO PROTECT YOUR TOPOLOGY TO RECEIVING ANY BPDU
4. ROOT GUARD FEATURE ENABLE ONLY BETWEEN ROOT AND NON
ROOT BRIDGE SWITCH AND NEVER USE IT BETWEEN PRIMARY AND
SECONDRY ROOT BRIDGE.

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1 Answers  

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