From: Colin Barber (Colin.Barber@xxxxxxxxxxxxxx)
Date: Wed Aug 28 2002 - 13:40:20 GMT-3
It may depend on the hardware involved. If the sup contains a NFFC then I
believe that spanning tree can only be disable completely on the switch, not
per vlan. If this is the case you are now affecting other parts of the
network.
The trouble with a lot of the lab scenarios out there is that they are not
very well written. The author may well be thinking of setting the priority
higher than anything else on the network and then wrote the question without
thinking of other possibilities/problems that question may bring.
Hopefully the real labs are written better. I would ask the proctor and if
they said 'read it again' or 'all the information you need is in the
question' then I would take it that never means never.
If you do need to make sure the cat is NEVER the root then yes the only
option is disabling spanning tree. This doesn't even test you knowledge of
spanning tree that well. Think of a single cat network, with no routers with
bridging enabled, and as long as spanning tree is enabled it will be the
root.
Where does this question come from? It has been brought up on the list many
times now, what is the authors solution?
Colin
-----Original Message-----
From: Jim Brown [mailto:Jim.Brown@caselogic.com]
Sent: 28 August 2002 17:22
To: 'Colin Barber'; 'Zhang, Ou (David)'; 'ccielab@groupstudy.com'
Subject: RE:
I would disagree with you on which answer is correct from a testing
standpoint. The word 'never' means to me, there must be no way the bridge
could become the root.
It you set the spantree priority as high as possible the switch could still
become the root. Bridges with duplicate spantree priorities then select the
root based on the MAC address.
I don't think the proctors would clarify this requirement anymore than
saying "read it again."
This is one of those questions that tests if you understand root bridge
selection and spanning tree priority.
Through our discussion of it on the list, we have effectively "dumbed down"
the requirement.
-----Original Message-----
From: Colin Barber [mailto:Colin.Barber@telewest.co.uk]
Sent: Wednesday, August 28, 2002 9:01 AM
To: 'Zhang, Ou (David)'; 'ccielab@groupstudy.com'
Subject: RE:
This have been discussed a few times before on this list.
The two options are the two you have listed. The first is I believe the
answer they are looking for although it does not guarantee 100% that the cat
will not become the root. The other option is not a very smart move although
a lot of the things we do in these labs are not very smart.
The best answer is ask the proctor if you get something like this in the
actual lab. If it's not the real lab then it doesn't matter which option you
take as long as you know both options and the pros/cons of each one.
Colin
-----Original Message-----
From: Zhang, Ou (David) [mailto:OuDavid.Zhang@gs.com]
Sent: 28 August 2002 14:57
To: 'ccielab@groupstudy.com'
Subject:
Hi,
Please help me with the answer for this question: Ensure that a Catalyst
5000 switch never becomes the root bridge for a given vlan.
I see two possible answers because I find the question ambiguous. Does it
mean 'the vlan can still run spanning tree without ever becoming the root',
or 'the vlan does will no longer run spanning tree'?
1. Set the spantree bridge-priority for the vlan to the highest possible
value.
!
set spantree priority 65535 <vlan#>
!
2. Disable spantree altogether for the vlan.
!
set spantree disable <vlan#>
!
Thanks.
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