vlan.dat file

[daudparvez]

Is vlan.dat file only created and maintained on the Server switches or also on the Client and Transparent Mode Switches?

Best Regards,

Daud Parvez.

[Peter Paluch]

Hello Daud,

Under Cisco IOS, the vlan.dat file is maintained on all switches, regardlessly of the VTP mode (Server, Client or Transparent).

Under the older Catalyst OS (CatOS), the vlan.dat was maintained if the switch was running VTP Server mode. I believe that the VTP Client and VTP Transparent mode did not utilize the vlan.dat file under CatOS. This difference between IOS and CatOS has proven to be a source of much confusion regarding the vlan.dat file. In any case, the CatOS is discontinued and all recent Catalyst switching platforms are using IOS-based operating system.

Best regards,

Peter

[daudparvez]

Dear Peter,

Thanks for your reply.

However, In CCNP book it has been mentioned that if the VTP Mode of a switch is changed to Transparent, the Revision No. is reset to 0 (vlan.dat ) file is deleted.

Isn't that mean that Transparent Switched do not have vlan.dat file?

Also, it has been written in the CCNP book that Client switches do not maintain the vlan.dat file and alwasy rely on servers to update them about the vlan database. That's something confusine me.

Best Regads,
Daud Parvez.

[Peter Paluch]

Hello Daud,

However, In CCNP book it has been mentioned that if the VTP Mode of a 
switch is changed to Transparent, the Revision No. is reset to 0 
(vlan.dat ) file is deleted.

It is true that setting a switch to VTP Transparent mode causes the revision to be set to 0. However, the vlan.dat file will not be deleted. On the contrary, the current VTP mode (the transparent mode) and the revision of 0 will be stored into that file.

Isn't that mean that Transparent Switched do not have vlan.dat file?

No, that is not correct. Even VTP Transparent switches do have the vlan.dat file and they store the entire VLAN database including the current VTP mode, revision, VTP domain name (still used in DTP), VTP password (although unused in transparent mode), VTP version setting and possibly other data in the file. It may sound a little strange but that's how it is currently done.

Also, it has been written in the CCNP book that Client switches do not 
maintain the vlan.dat file and alwasy rely on servers to update them 
about the vlan database. That's something confusine me.

That may have been true for CatOS based switches. However, this does not apply to IOS-based switches. Clearly, the authors of the CCNP book are using outdated information.

Best regards,

Peter

[Amit Singh]

I agree with Peter on this. In the CCNA and CCNP course, they always refer (i could be wrong) to CatOS as that was the primarily a Layer2 OS from Cisco initially. They always consider IOS as L3 OS in their old books. This needs to be updated and the behaviour what Peter is talking about is the correct and expected one on the Cisco IOS switches.

Cheers,

-amit singh

[milan.kulik]

Hi,

ad  "..it has been written in the CCNP book that Client switches do not maintain the vlan.dat file and alwasy rely on servers to update them about the vlan database."

This was correct several years ago with old IOS on XL switches, e.g.

But not correct for the current IOS.

HTH,

Milan

[Peter Paluch]

Hi Milan,

Thanks for updating this thread. This info is most valuable!

Best regards,

Peter