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New Member

Losing contact with 3550 when switching from VTP client to transparent mode

We have multiple cases of 3550 switches setup like this (pure L2):

outside world - 3550 VTP server - 3550 VTP client - 3550 VTP client

with VLAN trunks between the switches. If I am connected from the

outside to one of the 3550 VTP clients, and change VTP mode to

transparent, I lose contact with the switch (session freezes). As

soon as *all* switches are set to VTP transparent, my original

session is okay again. This is reproducible.

Any idea of why changing from VTP client to transparent would make

the session freeze?


Re: Losing contact with 3550 when switching from VTP client to t

In the case of a network like this,if a switch is suddenly changed to transparent mode ,the following conditions can happen.

1)If pruning is enabled, the trunks will go down.

2)If trunks go down and no other ports are in that VLAN, the VLAN interface in the installed Multilayer Switch Feature Card (MSFC) will go down.

If the effects described above occur, your network could be negatively affected if, for example, this switch is in the core of your network.

If you want more information on this ,you can follow the following URL:

New Member

Re: Losing contact with 3550 when switching from VTP client to t

Found the answer myself. This is VLAN pruning in action. With one end

of the link a VTP server or client, the other end VTP transparent, and

VLAN pruning enabled (by default), the VLANs on the VTP transparent

switch will be pruned. "switchport trunk pruning vlan none" will fix it.

You better know exactly which VLANs go where if you're going to use

this, of course.

New Member

Hello,Thanks. That's working


Thanks. That's working and is not disruptive for making cohabit VTP transparent, server, client switches and vtp pruning .

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