From: Harris, Joe F (Joe_Harris@xxxxxxxxxxxx)
Date: Mon Aug 06 2001 - 17:56:28 GMT-3
Actually, The port does not go directly into forwarding mode because if you
have left any of your channeling commands to the default the state of the
port is set to auto mode for etherchanneling and PAGP will run on the port
and not release it to spanning tree for about 15-18 seconds. You can test
this. If you use the "set port host mod/port" macro it will set the channel
mode to off on the ports that you specified in the "set port host" command
and then the port will go straight to a spanning-tree state of forwarding.
There are actually two types of BPDU's that the catalyst sends/receives,
Configuration BPDU's (most commonly known)which are sent out from the root
bridge and Topology Change Notification BPDU's that are sent to the root
bridge, TCN BPDU's are key to understanding another part of the portfast
feature. The TCN BPDU's are sent out in the event that the bridge detects a
change in its active topology and sets its CAM table age-out time to the
configured time of Forward delay. So by setting the port to portfast, the
switch no longer considers the port part of the active topology in which it
must monitor. If you use the portfast feature the port still participates in
STP though so that in the event that if the port is to be a part of the
loop, it will eventually transition into STP blocking mode. You should also
use the "portfast BPDU guard" feature on your switch port that have portfast
enabled. However the intitial question asked if it was possible to disable
BPDU transmitions on a VLAN basis and portfast only works on a per port
basis not per VLAN. In order to actually turn off all BPDU transmittions you
must disable spanning tree all together for that VLAN.
-Joe Harris
CCIE# 6200
-----Original Message-----
From: Padhu (LFG) [mailto:padhu@steinroe.com]
Sent: Monday, August 06, 2001 2:56 PM
To: 'Prashant Karunakaran'; Alex Fayn
Cc: ccielab@groupstudy.com
Subject: RE: BPDU on cat 5000
PORTFAST bypasses listen and learn and goes direct into fwd mode. Very good
when you have DHCP clients and avoid timeout issues on certain nics.
BPDUs are part of spantree...if disabled wouldn't send anything.
Cheers,padhu
-----Original Message-----
From: Prashant Karunakaran [mailto:pkarunak@cisco.com]
Sent: Friday, August 03, 2001 5:48 PM
To: Alex Fayn
Cc: ccielab@groupstudy.com
Subject: Re: BPDU on cat 5000
I think its set spantree portfast . Check the options available with
this command
Prashant
Alex Fayn wrote:
> Does anybody know how to turn off BPDUs on the Vlan ? Thank you.
>
> Alex
>
> Regards,
>
> Alex Fayn
>
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