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CCNA and CCNP candidates who have their own Cisco residence labs frequently e mail me about an odd circumstance that occurs when they erase a switch's configuration. Their startup configuration is gone, as they count on, but the VLAN and VTP information is nevertheless there!

Sounds strange, does not it? Let's look at an instance. On SW1, we run display vlan short and see in this abbreviated output that there are 3 additional vlans in use:

SW1#show vlan br

ten  VLAN0010                         active

20  VLAN0020                         active

30  VLAN0030                         active

We want to absolutely erase the router's startup configuration, so we use the create erase command, confirm it, and reload with no saving the operating config:

SW1#write erase

Erasing the nvram filesystem will take away all configuration files! Continue?

[confirm]

[OK]

Erase of nvram: complete

00:06:00: %SYS-7-NV_BLOCK_INIT: Initalized the geometry of nvram

SW1#reload

System configuration has been modified. Conserve? [yes/no]: n

Proceed with reload? [confirm]

The router reloads, and right after exiting setup mode, we run show vlan short yet again. And even although the startup configuration was erased, the vlans are nevertheless there!

Switch#show vlan br

ten  VLAN0010                         active

20  VLAN0020                         active

30  VLAN0030                         active

The cause is that this vlan and VTP data is truly kept in the VLAN.DAT file in Flash memory, and the contents of Flash are kept on a reload. The file has to be deleted manually.

There's a little trick to deleting this file. The switch will prompt you twice to ask if you truly want to get rid of this file. Do not type "y" or "yes" just accept the defaults by hitting the return essential. If you variety "y", the router attempts to delete a file named "y", as shown here:

Switch#delete vlan.dat

Delete filename [vlan.dat]? y

Delete flash:y? [confirm]

%Error deleting flash:y (No such file or directory)

Switch#delete vlan.dat

Delete filename [vlan.dat]?

Delete flash:vlan.dat? [confirm]

Switch#

The finest way to prepare for CCNA and CCNP exam success is by operating on true Cisco equipment, and by performing lab tasks more than and over. Repetition is the mother of ability, and by really erasing your VLAN and VTP details by deleting the vlan.dat file from Flash, you'll be constructing your Cisco expertise to the point where your CCNA and CCNP exam success is a certainty. cheap vespa scooters