switch in vtp client mode

[sarahr202]

hi every body!

Does switch in vtp client mode stores config revision number in vlan.dat or nvram?

i find some cisco documents which say client switch store config revision number in vlan.dat on flash while my cisco press book says client switch stores config revision number in nvram

which one is correct?

thanks a lot and have a nice day!

[Edison Ortiz]

The Cisco Press Book is correct.

http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_44_se/configuration/guide/swvtp.html#wp1035285

If you configure the switch for VTP client mode, the switch does not create the VLAN database file (vlan.dat). If the switch is then powered off, it resets the VTP configuration to the default. To keep the VTP configuration with VTP client mode after the switch restarts, you must first configure the VTP domain name before the VTP mode.

HTH,

__

Edison.

[sarahr202]

thanks for your reply. I think switch in client mode store vlan and vtp information in vlan.dat. Is it correct?

thanks!

[Edison Ortiz]

No, NVRAM.

Vlan.dat is used on VTP Servers.

__

Edison.

[sarahr202]

thanks for your reply! you mean switch in client mode

1) store vlan information and vtp information in nvram

or

does not store at all vlan information just vtp information in nvram.

thanks a lot!

[Edison Ortiz · Accepted solution]

I mean this

store vlan information and vtp information in nvram

All the information is obtained from the current VTP Server(s). If you turn off a VTP Client switch and turn it back on w/o VTP Server(s) being available, the switch won't have any Vlan information.

__

Edison.

[sarahr202]

Thanks Edison!

[sarahr202]

sorry to bother you.

nvram does not lose its contents upon reboot. So if the client switch store vlan and vtp information in nvram, and we turn off the switch in server mode and reboots the client switch, it should have vlan information because vlan information was stored in nvram.

thanks a lot!

[Edison Ortiz]

Stand corrected and I must word my answer better, the information technically isn't saved anywhere in the VTP Client as the device request this information from the VTP Server as needed.

Sarah, you deserve some rating :)

__

Edison.

[sarahr202]

thanks a lot Edison for your kind remarks!

So switch in client mode stores only vtp domain and config revision number in nvram?

Does it require the use of " copy running-config startup-config" ?

thanks a lot!

[Edison Ortiz]

According to this link

http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_35_se/configuration/guide/swvtp.html#wp1205076

It isn't saved anywhere. If the information is saved, it can be reused later but as you know, a reboot of the switch in an isolated area will result a switch w/o vlan information.

__

Edison.

[sarahr202]

Sorry Edison for this long post!

The link you forwarded says no vlan information is stored in nvram (if the switch in client mode).

It does not say anything about vtp information if it is stored or not.

However, before i posted my question , i read few cisco documents which say switch in client mode store vtp domain name and config revision number in nvram. Those documents do not say anything how this vtp information is saved i.e Do we need to use Copy running-config startup-config or switch in client mode automatically stores vtp informartion in nvram.

thanks a lot!

[darren-carr]

sarah202,

If in client mode the vlan info is not stored in NVRAM. If the switch is rebooted it will lose the VLAN info and will relearn it if it can access a VTP server in the same VTP domain when it loads. If it cannot contact a VTP server it will not learn the VTP domain information.

If configured VTP transparent (after being configured as a client initially) the file is saved into NVRAM so if rebooted the VLAN data will remain the same. Only issue with this is that if the VLAN info is changed on the server it will not auto update. You need to change the mode back to client for it to update then back to transparent to store the new config in NVRAM.

If configured as a server you can edit the vlan info, etc and it can push this out to your clients.

In our environment we have two VTP servers, the rest of the switches are saved as transparent with pruning enabled.

Benefit of this is that we only maintain one server for updating the VLAN info, we do have to change each switch to client thought to propogate the change to the network but this gives us control over who can do what and stops the network from being destroyed!!! :)

Hope this helps

Darren

[Edison Ortiz · Accepted solution]

Sarah,

I really praise you for your quest in obtaining the right information.

It inspired me to test this behavior in the lab and my results concluded the VTP information is held in the vlan.dat file.

I had a switch running in VTP Client mode and after deleting the vlan.dat file, the switch reverted back to VTP server after reboot.

In conclusion, the switch VTP status information is held in Vlan.dat while the Vlan information is provided by the VTP server.

Thanks for making me re-learn one of those obscures behavior within VTP.

Regards,

__

Edison.

[sarahr202]

Thanks a lot for your kind remarks Edison!

I have no resources to afford school or buy equipments. My teachers are people like you on this net pro and my book.

Anyway now I know the location where switch in client mode store vtp information. It is very discouraging that cisco own documents are full of contradictions .

According to following link:

{under the "common issues" link in the flash)

http://www.cisco.com/warp/public/473/vtp_flash/

switch in client mode does not store any vlan information ,rather it depends upon vtp server to receive vlans informations.

In the above flash, a swicth in client mode , with higher config revision number, is inserted in a domain to demonstrate how it will bring the network down.

The only problem is ,client switch inserted in the domain , still had vlans 200-300, with high config revision number.

My point as client switch does not store vlan informations, how come the inserted switch in client mode still had vlans 200-300, It should have only default vlan i.e vlan 1 nothing else.

Any comment will be greatly appreciated.

Thanks a lot and have a nice day!