[c-nsp] VTP and Vlan 1

[Michel Grossenbacher]

A little correction on my answer, VTP does not use the Native VLAN :-)

Here is what I found regarding the use of VTP and VLAN1:
The Case of VLAN 1

You cannot apply VTP pruning to VLANs that need to exist everywhere and that
need to be allowed on all switches in the campus, in order to be able to
carry VTP, Cisco Discovery Protocol [CDP] traffic, and other control
traffic. However, there is a way to limit the extent of VLAN 1. The feature
is called VLAN 1 disable on trunk. The feature is available on Catalyst
4500/4000, 5500/5000, and 6500/6000 series switches in CatOS software
release 5.4(x) and later. The feature allows you to prune VLAN 1 from a
trunk, as you do for any other VLAN. This pruning does not include all the
control protocol traffic that is still allowed on the trunk (DTP, PAgP, CDP,
VTP, and others). However, the pruning does block all user traffic on that
trunk. With this feature, you can keep the VLAN from spanning the entire
campus. STP loops are limited in extent, even in VLAN 1. Configure VLAN 1 to
be disabled, as you would configure other VLANs to be cleared from the
trunk:

UDLD uses native VLAN in order to talk to the neighbor. So, in a trunk port,
the native VLAN must not be pruned in order for UDLD to work properly.
http://www.cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080890613.shtml

Sorry for the confusion.

best regards

Michel


On 25/08/2008, Michel Grossenbacher <pashtuk at gmail.com> wrote:
>
> Hi Mike
> Actually VLAN 1 is not pruning-eligible so you can not prune VLAN 1 from a
> trunk. However you can remove it from the trunk.
> If you remove it from the trunk and change the native VLAN for the trunk,
> VTP will then use the new native VLAN for updates.
> best regards
>
> Michel
>
>
>  On 25/08/2008, Mike Louis <MLouis at nwnit.com> wrote:
>>
>> List,
>>
>> I just read in a practice test for an upcoming cert that Vlan 1 is used to
>> carry VTP advertisements. However, it is possible to prune vlan 1 from trunk
>> links. Will VTP continue to function without Vlan 1 being enabled on the
>> link? Has this changed in more recent IOS releases?
>>
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