Cisco Vlan Query

Unanswered Question
Apr 1st, 2012

Hi Experts,

Can someone explain to me why I can't see the vlan  100 and name user-vlan in the show run in the first attachment, however I  can see it when I do a show vlan brief? However, the second attachment I  can see the vlan in the show run/configuration.

The reason why I  ask is because when I do a copy the configs from a TFTP to the switch  in the first case the vlan 100 and name user-vlan won't be copied to the  switch because its not in configuration, whereas in the second case the  vlan configurations will be picked up and copied to the switch because  its in seen in the configurations

Cheers

Carlton

I have this problem too.
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rustom.cisco Sun, 04/01/2012 - 08:05

Hi Carlton,

Vlan databases for Most Cisco switches are not stored in the config files (startup or running config). They are stored in a seperate file which does not exist on teh nvram as most configuartions do. instead they are stored on a file with the name of "vlan.dat". This file can be found on the flash of your switch. Hence even if you were to erase the nvram and reload the routers, the Switch vlan databased would still showup the old vlans.

Regards,

Rustom Billimoria,

CCIE RS#24798

carltonpatterson Sun, 04/01/2012 - 08:40

Thanks for responding.

I understand what you're saying. It just seemed weird that the vlan information showed in one running config but not in the other.

You think it might be because on switch I configured vtp version 2, vtp domain switch, vtp pass ccnp?

Just a thought...

Peter Paluch Sun, 04/01/2012 - 10:34

Hello Carlton,

What you are seeing here is caused by your VTP mode setting. If the VTP mode is set to Transparent then the VLANs are being displayed in the running-config in addition of being also stored in the vlan.dat file. If the VTP mode is either Server or Client, the VLANs are only stored in the vlan.dat file and do not appear in the running config. As you can see, your second configuration obviously contains the vtp mode transparent command.

Best regards,

Peter

glen.grant Sun, 04/01/2012 - 10:35

  Because one unit is probably setup as a vtp server   and the other unit is setup as vtp transparent.  Only units that are setup as transparent will have the the vlan information in the running config  otherwise that info is just stored in vlan.dat and not visible in the config.

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