CCNA and CCNP candidates who have their own Cisco residence labs usually e mail me about an odd state of affairs that occurs once they erase a swap’s configuration. Their startup configuration is gone, as they anticipate, but the VLAN and VTP info is still there!
Sounds strange, doesn’t it? Let’s take a look at an example. On SW1, we run present vlan temporary and see on this abbreviated output that there are three extra vlans in use:
Switch#show vlan br
10 VLAN0010 active
20 VLAN0020 active
30 VLAN0030 active
The reason is that this vlan and VTP information is actually 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 really want to get rid of this file. Don’t type “y” or “yes”; just accept the defaults by hitting the return key. If you type “y”, the router attempts to delete a file named “y”, as shown here:
Delete filename [vlan.dat]? y
Delete flash:y? [confirm]
%Error deleting flash:y (No such file or directory)
Delete filename [vlan.dat]?
Delete flash:vlan.dat? [confirm]
The best way to prepare for CCNA and CCNP exam success is by working on real Cisco equipment, and by performing lab tasks over and over. Repetition is the mother of skill, and by truly erasing your VLAN and VTP information by deleting the vlan.dat file from Flash, you’ll be building your Cisco skills to the point where your CCNA and CCNP exam success is a certainty.