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Posted by Merv on April 17, 2008, 1:41 pm
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>
>
> > > is there anything wrong (not sure if possible) with setting up 5 vlans
> > > (vlan 1,2,3,4,5) on the first 2950 switch and just 2 vlans (vlan 1,6)
> > > on the second 2950 switch? There will be a trunk between 3750 to each
> > > of the 2950.
>
> > Perfectly fine AFAIK
>
> > Do yourself a favour and avoid the use of VTP; manually configure the
> > VLANs in use on each switch.
>
> > Also ditch DTP
>
> > Use the command "switchport trunk allowed vlan [allowed vlans] " on
> > the trunk ports on the 3750
> > and configure the VLANS in the command that are on each of the 2950's
>
> > Enable CDP on trunk ports; disable on all other ports
>
> > interface <>
> > description Switch Trunk
> > switchport trunk encapsulation dot1q
> > switchport trunk allowed vlan [allowed vlans]
> > switchport mode trunk
> > switchport nonegotiate
> > cdp enable
>
> Is there any other reason you are suggesting avoiding VTP beyond the
> obvious 'gotcha' with deploying switches w/ higher revision numbers?
> While most environments are heading towards distributed layer 3 where
> trunking is a thing of the past (except between access pairs), I still
> know of tons of companies running very large layer 2 networks. While
> VTP does have a major gotcha that should be well-known to any network
> designer/engineer, I don't necessarily agree that avoiding it
> altogether is the answer, particularly for companies with decent sized
> network groups (multiple engineers doing different things). Who wants
> to maintain updating vlan names on every switch in a 50 switch
> datacenter? Additionally, what stops you from then using the same
> number more than once if you have strict pruning guidelines which can
> cause issues if they ever need to be extended. I suppose you could
> make the update part of the process of trunking out and/or removing
> pruning, but just seems like an unnecessary headache.
>
> Perhaps I am missing something major since its early AM, but its not
> the first time i have seen that advice and wondered.
the OP with a small network is best to avoid all the benefits of
VTP ;-))
from Cisco best practice doc
http://www.cisco.com/en/US/products/hw/switches/ps700/products_white_paper09186a00801b49a4.shtml#cg1
"
There are pros and cons to the VTP ability to make changes easily on a
network. Many enterprises prefer a cautious approach and use VTP
transparent mode for these reasons:
This practice encourages good change control because the requirement
to modify a VLAN on a switch or trunk port must be considered one
switch at a time.
VTP transparent mode limits the risk of an administrator error, such
as accidental deletion of a VLAN. Such errors can impact the entire
domain.
VLANs can be pruned from trunks down to switches that do not have
ports in the VLAN. This results in frame flooding to be more bandwidth-
efficient. Manual pruning also has a reduced spanning-tree diameter.
See the Dynamic Trunking Protocol section for more information. A per-
switch VLAN configuration also encourages this practice.
There is no risk of the introduction into the network of a new switch
with a higher VTP revision number that overwrites the entire domain
VLAN configuration.
Cisco IOS Software VTP transparent mode is supported in Campus Manager
3.2, which is part of CiscoWorks2000. The earlier restriction that
requires you to have at least one server in a VTP domain has been
removed.
"
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