Unable to See VLAN Details in the show run Command Output
VTP client and server systems require VTP updates from other VTP servers to be immediately saved without user intervention. A VLAN database was introduced into Cisco IOS Software as a method to immediately save VTP updates for VTP clients and servers. In some versions of software, this VLAN database is in the form of a separate file in Flash, called the vlan.dat file. You can view VTP and VLAN information that is stored in the vlan.dat file for the VTP client or VTP server if you issue the show vtp status command.
VTP server and client mode switches do not save the entire VTP and VLAN configuration to the startup-config file in NVRAM when you issue the copy running-config startup-config command on these systems. VTP saves the configuration in the vlan.dat file. This behavior does not apply to systems that run in VTP transparent mode. VTP transparent
Figure 2-40 VTP Troubleshooting
switches save the entire VTP and VLAN configuration to the startup-config file in NVRAM when you issue the copy running-config startup-config command. For example, if you delete the vlan.dat file on a VTP server or client mode switch after you have configured VLANS, and then you reload the switch, VTP is reset to the default settings. (All user-configured VLANs are deleted.) But if you delete the vlan.dat file on a VTP transparent mode switch and then reload the switch, it retains the VTP configuration. This is an example of default VTP configuration.
You can configure normal-range VLANs (2 through 1000) when the switch is in either VTP server or transparent mode. But on the Cisco Catalyst 2960 switch, you can configure extended-range VLANs (1025 through 4094) only on VTP-transparent switches.
Continue reading here: Cisco Catalyst Switches Do Not Exchange VTP Information
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