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RE: bpdufilter logic posted 11/19/2006
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The bpdufilter actually works with 'switchport portfast' command in global
mode (in interface mode as well but behavior is slightly different than in
global mode), also keep that in mind that portfast is enabled for access
hosts not for other L2 devices with spanning tree on as it can result in
loops. So bpdufilter disables portfast on an interface as soon as it
receives a bpdu on that interface and re-enables the spanning tree
calculation (on that particular interface only) to prevent any looping.

To summarize, bpdufilter just disables portfast feature on an interface if
it receives bpdus on that interface. 

Hope it clarifies.


-----Original Message-----
From: nobody@xxxxxxxxxxxxxx [mailto:nobody@xxxxxxxxxxxxxx] On Behalf Of
Alexey Tolstenok
Sent: Sunday, November 19, 2006 8:58 PM
To: Cisco certification
Subject: bpdufilter logic

What idea is behind bpdufilter? :
(From DocCD)

If a BPDU is received on a Port Fast-enabled interface, the interface loses
its Port Fast-operational status, and BPDU filtering is disabled.

Hmm filtering is disabled when receiving BPDUs?
I'm confusing....

SY, Alexey

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