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!
During my test, I also found the VTP Client keeps the Vlans that were obtained from the VTP server.
All that information is tied together in the vlan.dat file so indeed - a VTP Client can bring a network down in some situations such as 'higher revision number'.
Best Practice is to delete the vlan.dat file on any new switch being inserted into a production network.
Keep hitting those books, you are bringing up very useful topics into these forums :)
Here is some output from an isolated switch:
S4#sh vtp status
VTP Version : 2
Configuration Revision : 14
Maximum VLANs supported locally : 1005
Number of existing VLANs : 14
VTP Operating Mode : Client
VTP Domain Name : NET34
Trying to create a Vlan:
VTP VLAN configuration not allowed when device is in CLIENT mode.
No other switch connected:
S4#sh int trunk
Vlans obtained from a VTP Server before rebooting:
S4#sh vlan | e unsup
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4
Fa0/5, Fa0/6, Fa0/7, Fa0/8
Fa0/9, Fa0/10, Fa0/11, Fa0/12
Fa0/13, Fa0/14, Fa0/15, Fa0/16
Fa0/17, Fa0/18, Fa0/19, Fa0/20
Fa0/21, Fa0/22, Fa0/23, Fa0/24
4 VLAN0004 active
10 VLAN_10 active
40 VLAN0040 active
45 VLAN0045 active
49 VLAN0049 active
50 VLAN0050 active
59 VLAN0059 active
100 VLAN0100 active
363 VLAN0363 active
BTW, I deleted NVRAM: "startup-config" and "private-config" files and it deleted my original configuration but the Vlan information was kept intact since they are kept in Vlan.dat as I previously stated.
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.
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.