Giuseppe Larosa Tue, 06/23/2009 - 05:14

Hello Darren,

it should work well

I've seen that at least recent IOS based switches when moving to VTP transparent mode retain the list of vlans they had learned.

Actually modern VTP clients keep the list of vlans somewhere so even if they are powered on stand-alone they keep the last list of vlans.

Hope to help


tandlauer Tue, 06/23/2009 - 05:30

Hi everybody,

Giuseppe is right, the Vlan databases of the Client switches don't disappear when you pass in transparent mode. Just the revision number is reseted in this case. In client mode, a switch record the vlan database in memory (RAM) so if you reboot, all the database is lost and relearned if it still client.

When you pass in transparent mode, just make sure the file vlan.dat is present as on many switch models, the VTP configuration is recorded in this file. In some other models, the VTP and Vlan configuration is recorded in the startup-config.



Your solution will work fine. Once in transparent mode, your switches will be aware of the VTP domain but will not participate. If you wanted to, you could change the VTP domain name on the non-participating switches to a new (unused) domain, and then clear out the unneeded vlans from within the local database. Hope this helps.

darrenriley5 Wed, 06/24/2009 - 01:37

Thanks, changing the vtp domain should add an extra layer of security so the vlans can't be deleted by accident. Just to confirm if I change the vtp domain while in transparent mode the switch will keep its vlan database? My plan now is to

1)change vtp mode of clients to transparent

2) change vtp domain to new (unused domain)

3) remove unused vlans


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