NoellDetwiler421

CCNA and CCNP candidates who have their own Cisco property labs typically e mail me about an odd scenario that happens when they erase a switch's configuration. Their startup configuration is gone, as they expect, but the VLAN and VTP details is nevertheless there!

Sounds odd, doesn't it? Let's look at an instance. On SW1, we run show vlan short and see in this abbreviated output that there are 3 further vlans in use:

SW1#show vlan br

10 VLAN0010 active

20 VLAN0020 active

30 VLAN0030 active

We want to absolutely erase the router's startup configuration, so we use the publish erase command, confirm it, and reload without having saving the running config:

SW1#compose erase

Erasing the nvram filesystem will get rid of all configuration files! Continue?

[confirm]

[OK]

Erase of nvram: comprehensive

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

SW1#reload

Program configuration has been modified. Save? [yes/no]: n

Proceed with reload? [confirm]

The router reloads, and following exiting setup mode, we run display vlan short again. And even although the startup configuration was erased, the vlans are nonetheless there!

Switch#show vlan br

10 VLAN0010 active

20 VLAN0020 active

30 VLAN0030 active

The reason is that this vlan and VTP information 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 is a small trick to deleting this file. The switch will prompt you twice to ask if you actually want to get rid of this file. Do not type "y" or "yes" just accept the defaults by hitting the return key. If you sort "y", the router attempts to delete a file named "y", as shown right 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 accomplishment is by working on actual Cisco equipment, and by performing lab tasks over and more than. Repetition is the mother of skill, and by really erasing your VLAN and VTP info by deleting the vlan.dat file from Flash, you are going to be building your Cisco abilities to the point where your CCNA and CCNP exam achievement is a certainty. used cars dealers