From: Huan Pham (pnhuan@yahoo.com)
Date: Mon Dec 22 2008 - 18:19:55 ARST
Hi Lloyd,
I think the Cisco accessor lab is also covered by NDA. Do not mention any
specific details of the exam you take. In stead, you should have only
discussed your misunderstanding in a general context.
Enable portfast does not disable spanning tree. The port just bypasses the
spanning tree states when the first turn from down to up (when you unshut the
port, or when the switch first boots up)
The proof to show that portfast does not disable spanning-tree is when you do
"show interface switchport details"
you will see that the port still sending BPDU, and may receive BPDU as well.
Upon receiving a BPDU, the port may turn to err-disable for that VLAN, for the
whole physical port (i.e. all VLANs), or restarting normal spanning tree
states of blocking, listening, learning, and forwarding, depending on other
features you configure with (e.g. bpduguard, bpdufilter) and whether you
configure the portfast in global or interface level.
Please check command reference for: "spanning-tree portfast" for futher
details.
If the question asks to disable spanning-tree, I may have a few solutions:
- Shutdown the port, whether it violates other requirements is another story.
- Turn the port to routed mode, i.e. no switchport
- Spanning bpdufilter
I think you may have other solutions as well.
Cheers,
Huan
--- On Tue, 12/23/08, Lloyd Ardoin <Lloyd@TheWizKid.biz> wrote:
From: Lloyd Ardoin <Lloyd@TheWizKid.biz>
Subject: Disable Spanning-tree
To: "ccielab@groupstudy.com" <ccielab@groupstudy.com>
Date: Tuesday, December 23, 2008, 6:42 AM
Hi GS,
I was doing a Cisco ASET lab yesterday and came across a switching task that
basically said that hosts were connected to ports fa0/12 - 14 in VLAN 13 and
they wanted you to configure the ports in such a way to have them come up as
quickly as possible without turning off spanning-tree. My solution was to
reduce the timers for VLAN 13 to their minimums but the solution from Cisco
was to use the portfast command. I was under the impression that when you
applied the portfast command to a switchport it disabled spanning-tree for
that port. Is this a mis-understanding on my part?
thanks,
Lloyd
Blogs and organic groups at http://www.ccie.net
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