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Passing Cisco's CCNA and CCNP Exams The 'VLAN.DAT' File |
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CCNA and CCNP candidates who have their own Cisco home labs
often email me about an odd situation that occurs when they
erase a switch's configuration. Their startup configuration
is gone, as they expect, but the VLAN and VTP information
is still there!
Sounds strange, doesn't it? Let's look at an example. On
SW1, we run show vlan brief and in this abbreviated output
see that there are three additional vlans in use:
SW1#show vlan br
10 VLAN0010 active
20 VLAN0020 active
30 VLAN0030 active
We want to totally erase the router's startup configuration,
so we use the write erase command, confirm it, and reload
without saving the running config:
SW1#write erase
Erasing the nvram filesystem will remove all configuration
files! Continue? [confirm]
[OK]
Erase of nvram: complete
SW1#rel
00:06:00: %SYS-7-NV_BLOCK_INIT: Initalized the geometry of
nvram
SW1#reload
System configuration has been modified. Save? [yes/no]: n
Proceed with reload? [confirm]
The router reloads, and after exiting setup mode, we run
show vlan brief again. And even though the startup configuration
was erased, the vlans are still there!
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:
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 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.
About the Author:
Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage,
home of free CCNA and CCNP tutorials, The Ultimate CCNA Study
Package, and Ultimate CCNP Study Packages. For a FREE copy
of his latest e-books, “How To Pass The CCNA” and
“How To Pass The CCNP”, visit the website and download
your free copies. You can also get FREE CCNA and CCNP exam
questions every day! Pass the CCNA exam with The Bryant Advantage!
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