A VTP transparent mode switch between a VTP server and a client

From: Toh Soon, Lim (tohsoon28@gmail.com)
Date: Thu Jul 26 2007 - 06:47:54 ART


Hi,

Below is explanation on Cisco.com with regards to the behavior of a switch
in VTP transparent mode for VTP versions 1 and 2:

-----------------------------------------------------------
In VTP version 1, a VTP transparent switch inspects VTP messages for the
domain name and version and forwards a message only if the version and
domain name match. Because VTP version 2 supports only one domain, it
forwards VTP messages in transparent mode without inspecting the version and
domain name.
-----------------------------------------------------------

My question, in VTP ver 1 the switch only forwards a message if the version
and domain name match. I think the version number could never match because
it's always a 0 on a transparent mode switch.

Below is my simple setup to test the above theory:

SW1 -----(dot1q)----- SW2 -----(dot1q)----- SW3
All trunk config:
----------------------
!
int gig ...
 switchport trunk encapsulation dot1q
 switchport mode trunk
!

SW1
------
!
vtp mode server
vtp domain MYDOMAIN
!

SW2
------
!
vtp mode transparent
vtp domain NODOMAIN
vtp version 1
!

SW3
------
!
vtp mode client
vtp domain MYDOMAIN
!

With the above config, new VLANs created on SW1 are not synchronized to SW3.
Even after I reconfigured SW2 to "vtp version 2", VLANs are still not
synchronized.

When I reconfigured SW2 to "vtp domain MYDOMAIN", the VLANs from SW1 are
sync to SW3, regardless of whether SW2 is running VTP version 1 or 2.

Please advise.

Thank you.

B.Rgds,
Lim TS



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