http://www.cisco.com/en/US/products/hw/switches/ps663/products_tech_note09186a0080094713.shtml
The following is the Copy/Paste from the above link. It should put all
doubts regarding to rest about Vlan 1.
*
CDP, VTP, and PAgP updates are always forwarded on trunks with a VLAN
1 tag. This is the case even if VLAN 1 is cleared from the trunks and
is not the native VLAN. If VLAN 1 is cleared for user data, these is
no impact on control plane traffic that is still sent using VLAN 1.
*
On an ISL trunk, DTP packets are sent on VLAN1. This is the case even
if VLAN 1 is cleared from the trunk and is no longer the native VLAN.
On an 802.1Q trunk, DTP packets are sent on the native VLAN. This is
the case even if the native VLAN is cleared from the trunk.
*
In PVST+, the 802.1Q IEEE BPDUs are forwarded untagged on the common
Spanning Tree VLAN 1 for interoperability with other vendors, unless
VLAN 1 is cleared from the trunk. This is the case regardless of the
native VLAN configuration. Cisco PVST+ BPDUs are sent and tagged for
all other VLANs. Refer to the Spanning Tree Protocol section in this
document for more details.
*
802.1s Multiple Spanning Tree (MST) BPDUs are always sent on VLAN 1
on both ISL and 802.1Q trunks. This applies even when VLAN 1 is
cleared from the trunks.
*
Do not clear or disable VLAN 1 on trunks between MST bridges and
PVST+ bridges. But, in the case that VLAN 1 is disabled, the MST
bridge must become root in order for all VLANs to avoid the MST
bridge putting its boundary ports in the root-inconsistent state.
Refer to Understanding Multiple Spanning Tree Protocol (802.1s) for
details.
Desmond Black,
In Pursuit of CCIE!!
India
----- Original Message -----
From: "Kaj Niemi"
To: "Kim Pedersen"
Cc: "Online Study List"
Subject: Re: [OSL | CCIE_RS] Native vlan and manually pruning
Date: Fri, 21 Aug 2009 14:57:31 -0700
Hi,
Honestly I haven't labbed to see if native in this case is always
vlan 1 or
if it can be something else but it should work even if you prune it.
I'm
kind of betting on it having to be vlan 1 everywhere because IST (MST
instance 0) is the same as CST which is computed out of VLAN 1's
spanning
tree... IST is also the only one actually sends/receives BPDUs the
instance
configuration can be found within the MST BPDUs themselves.
:)
Kaj
cc: the list
> From: Kim Pedersen
> Date: Fri, 21 Aug 2009 14:15:26 -0700
> To: Kaj Niemi
> Subject: Re: [OSL | CCIE_RS] Native vlan and manually pruning
>
> In this discussion, what if the native vlan is manually pruned? :)
> or does it use also use vlan1?
>
> Also, are all the MISTs using the native vlan, or is it only IST0
(The
> CIST as i remember it)?
<< smime.p7s >>
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