How to add switches when VTP server already exists

[malberttoo]

My small network contains a single Cat 3560 switch, that has several vlans configured on it and it is also set as the VTP server.

I have a few newer Cisco switches that I want to add to the network. They have been configured by someone else for me via console and I have not yet plugged them into the network. I'm concerned that doing so could mess things up, with the existing switch being the VTP server. These newer switches have some vlans configured on them that the current switch does not. I do want to use these new vlans and want them to show up on all the switches. 

Should I configure something differently first before I plug any of the new switches in?  

Once the new switches are in service, what's the proper way to move the VTP server role from one switch to another?

Thanks for your time.

[Mark Malone]

Hi
be careful a higher revision number could wipe the other switch if its set as server too its a flaw in older vtp version 1 , what VTP version is running on both switches ? use a mimimum of vtp v2

I would set the new switches to transparent first then back to client that should set the revision number back to 0 if not already lower than current 3560 , you can see it in show vtp status

you could delete all the vlans off the new switches too you dont want , set them then to client same vtp domain etc so the vlans are passed down from current 3560 switch and it cant pass to server switch or leave it in transparent mode and just manually transfer them

You can have multiple VTP servers same lan but wouldnt recommend it, transparents the safest mode cant really break anything in that , once both switches have same vlans and vtp settings , its safe enough to set one to client and another to server without breaking anything

[malberttoo]

Hi, this my sh vtp status from the existing Cat 3560-

VTP Version : 2
Configuration Revision : 5
Maximum VLANs supported locally : 1005
Number of existing VLANs : 10
VTP Operating Mode : Server
VTP Domain Name :
VTP Pruning Mode : Disabled
VTP V2 Mode : Disabled
VTP Traps Generation : Disabled

And here it is from as configured from one of the new switches. All the new switches (outside of IP address etc) are identical-

VTP Version capable : 1 to 3
VTP version running : 1
VTP Domain Name :
VTP Pruning Mode : Disabled
VTP Traps Generation : Disabled
Device ID : 68bc.0c21.5f00
Configuration last modified by 0.0.0.0 at 3-1-93 09:31:01
Local updater ID is 0.0.0.0 (no valid interface found)

Feature VLAN:
--------------
VTP Operating Mode : Server
Maximum VLANs supported locally : 255
Number of existing VLANs : 10
Configuration Revision : 5

Eta-  I DO want the vlans that were configured on these new switches, to show up everywhere.

[Mark Malone]

Hi

dont use VTP version 1 even though the revision numbers are equal , i would set the switches to VTP trasnparent then back to client to reset the VTP revision to 0

(conf t)vtp ver 2

vtp mode transparent

vtp mode client

then check vtp status again revision should be 0

If you want the vlans to be everywhere , add them to the server switch and set the rest of the switches as VTP client , they will push out from the server to each switch

You will need to add a VTP domain name as well , make sure its same on each switch so they can speak to each other through VTP

VLANs should pass even server to server mode , but i would leave 1 as server the rest as client of your using VTP

Or set them all as trasnparent and manually handle it

[malberttoo]

Mark, thanks for the help.

With the VTP domain name, does is have to match anything specific already happening on the network? Or is this only going to be used with VTP?

[Mark Malone]

Hi
its only used in VTP thats it , you could call it anything like vtp.com just make sure each switch has it or they cant take part in the vlan sharing

[Andrew Khalil]

Hello @malberttoo,

Greetings,

It's a pleasure to support you!

Actually, any switch can be in 3 VTP modes (server, client and transparent)

The Idea that: (assuming that all switches have the same VTP domain and password) 

1- if you configure any switch as a server while others as clients, all clients will get the same vlans in the server one.

2- if you connected a new server switch to a network that has a server one already while all other in client mode, so the one with the highest revision number (I mean the 2 server switches) will be the effective one as a server, and all other clients will follow it regardless the one that was server before.

3- if you configured any switch as a transparent, and then you configure on it any new vlan, it will not be affecting the rest of switches.

For the best practice, you need to:

1- configure all switches with the proper vtp domain and password.

2- configure all switches as clients.

3- configure the one that have the desired vlans as a server.

4- make sure that the links in between the switches are in trunk mode.

I believe that I have answered you sufficiently, please don't hesitate if you will need any more support!

Please don't forget to rate all the helpful responses and mark solutions!

Bst Rgds,

Andrew Khalil 

[Dennis Mink]

if you have a small network and are not too inetersted in VTP. put them in transparent mode before you stick them into the network

[paul driver]

Hello

Just like to add -

A switch running as a vtp client with a higher revision number could also wipe your vtp database so as the other guys have mentioned before you attach any switch with old vtp config , suggest you at the very least change vtp mode to transparent and back to either server/client before you add it to the production estate..

[Joseph W. Doherty]

"Once the new switches are in service, what's the proper way to move the VTP server role from one switch to another?"

It depends on the VTP version you're running. With VTP versions 1 and 2, what a "server" allows is manual editing of the VLANs. The only risk of having more than one "server" with those version are, two switches might be manually edited at the same time, and they would both advertise their revision. If the revision number was the same, you could have consistency conflicts. The way to avoid that is to only have one switch in the "server" role. As to how to change it, just set the existing "server" to client, and the switch to be "server" to be server role.

For VTP version 3, I recall changing modes is more involved. I would need to consult the documentation for how they are maintained.

"They have been configured by someone else for me via console and I have not yet plugged them into the network. I'm concerned that doing so could mess things up, with the existing switch being the VTP server."

Yes, as noted by others, adding switches to your VTP domain, again if running VTP version 1 or 2, entails a chance of them resetting all your VTP VLAN information. Do note, switches do not need to be configured in "server" role, "client" role can reset your VTP VLAN information too.

Before adding switches, with VTP versions 1 or 2, as also noted by others, set VTP role to "transparent" (or in later IOS versions, to "off") mode. If you want them to join the VTP domain, configure the VTP domain name (BTW, if it's NUL, it will auto change) and configure the VTP password (if set), then configure role as "client".  Switch should replace it's VLAN information with that of the VTP domain. (NB: port VLAN settings won't change.) (Also BTW, VTP needs a trunk link to exist between switches.)

Again, for VTP version 3, I recall adding a client is also more involved (VTP v.3 is designed to preclude the accidental VTP resets of versions 1 and 2), and I would also need to review the documentation for how it's done.