VTP mode: Transparent

[bibekdeep]

It says in Mr. Lammle book that:

"the whole purpose of transparent mode is to allow remote switches to receive the VLAN database from a VTP server-configured switch through a switch that is not participating in the same VLAN assignments"

My question is, does this mean that the transparent mode can create, modify, and delete VLANs in other VLANs? or something else?

Please Explain

Please and thank you

[lammle]

This is an important CCNA objective.

VTP server can add, delete, modify VLAN's stored in the vlan.dat file, and will send summary advertisements out all trunked links.

Clients only receive summary advertisments from Servers, and will place the VLAN database only in RAM and forward the summary advertisments to downstream neighbors connected with a trunk link.

Transparent mode only recieves and forwards summary advertisments to downstreadm neighbors connected with a trunk link, but has it's own local VLAN database stored in flash in a file called vlan.dat. It does not process the summary advertisements from a server, only receives and forwards.

You can't really turn off VTP, so if you don't ever want to use VTP you should set all your switches to VTP transparent mode just so no problems can occur - and they can with VTP.

Cheers!
Todd Lammle

[bibekdeep]

I think I understand the gist of it.

However, there is one thing that am still pondering: why does transparent mode have its own VLAN database.

So basically, what purpose the transparent VLAN database serve?

or am I going beyond the CCNA objectives when I ask this?

[Big Evil]

Configuration changes in CatOS are written to NVRAM immediately after a change is made. In contrast, Cisco IOS?? Software does not save configuration changes to NVRAM unless you issue the copy running-config startup-config command. VTP client and server systems require VTP updates from other VTP servers to be immediately saved in NVRAM without user intervention. The VTP update requirements are met by the default CatOS operation, but the Cisco IOS update model requires an alternative update operation.

For this alteration, 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 NVRAM, called the vlan.dat file. You can view VTP/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/client mode switches do not save the entire VTP/VLAN configuration to the startup config file in the NVRAM when you issue the copy running-config startup-config command on these systems. It saves the configuration in the vlan.dat file. This does not apply to systems that run as VTP transparent. VTP transparent systems save the entire VTP/VLAN configuration to the startup config file in NVRAM when you issue the copy running-config startup-config command. For example, if you delete vlan.dat file after the configuration of the VTP in server or client mode and reload the switch, it resets the VTP configuration to default settings. However, if you configure VTP in transparent mode, delete the vlan.dat and reload the switch. This retains the VTP configuration.

HTH.

[lammle]

This document is no longer completely accurate.
It is from early 2007 and is even showing Token Ring translation and the set/clear command set on the switches - now that's old information.

VTP works slightly different today, and especially on the CCNA Objectives.
I wouldn't use this document to study for my CCNA that's for damn sure!
Thanks B.E.!
Todd

[Big Evil]

Thanks TL did not see the date.

[lammle]

No problem, VTP works different now than that document, and as I said, especially on the CCNA Objectives.
Todd Lammle

[Fuzz]

So basically, what purpose the transparent VLAN database serve?



Simply put, a transparent mode switch does not participate in the VTP domain, so in order to save the VLAN config in case of power failure/reboot etc, it stores the database in flash, just as server and client mode do. Essentially, it provides resilience.

Updating the VLAN database on a transparent mode switch only updates that switch's vlan.dat file. Updating the VLAN information on a server mode switch updates the vlan.dat file on all servers and clients in the domain.

Deleting the vlan.dat file wipes the VLAN/VTP information from the switch, regardless of what mode it is in. In practice, you would issue an erase startup, delete the vlan.dat, and reload the switch. This would bring the switch to factory default.