Re: question on port fast and bpdu guard

Thanks you Anthony & Cristian,

 i have the following topology

SWA--------------------------------------------SWB
   | |
   | |
   | |
   | |
   | |
SWC--------------------------------------------SWD

IS there a loop in the network.?? yes as each switch has tow different paths
to reach the other switch ..

*how does SWC or SWD know about the loop in the topology ..*

This was my interview question...i simply said " by examining BPDU'S.." but
he needed more detailed answers..

i am looking for more technical answer..

Thanks

On Thu, Apr 15, 2010 at 8:56 PM, Cristian Matei
<cristian.matei_at_datanets.ro>wrote:

> Hi Ali,
>
> BPDU Guard and BPDU Filter can be applied in the following 2 ways:
> -at the global level; once enabled here it will get applied
> only to PORTFAST enabled ports (I say enabled and not configured as a
> configured portfast port may lose its portfast status in certain
> conditions)
> -at the interface level; once enabled here it's just applied
> regardless of the portfast status of the port (so portfast is not required
> in this case)
>
> Now PORTFast itself is not "needed" for STP or RSTP; it just improves
> end-to-end STP/RSTP convergence time; for best end-to-end convergence time,
> PORTFAST is required to be explicitly configured in both STP and RSTP.
>
> Regards,
> Cristian.
>
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
> imran ali
> Sent: Thursday, April 15, 2010 5:49 PM
> To: Cisco certification
> Subject: question on port fast and bpdu guard
>
> HI gurus,
>
> does enabling bpdu guard requires a port fast to be enabled.. i mean bpdu
> guard can be enabled independent of port fast status ?.
>
> further why portfast is required in traditional STP topology and not in
> RSTP
> networks..??
>
> can i enable portfast feature in RSTP netorks
>
> Thanks,
>
>
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Received on Thu Apr 15 2010 - 21:48:56 ART