Passing Cisco's CCNA and CCNP Exams: The VLAN.DAT File

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Home \| Computers \| Networks \| Passing Cisco's CCNA ... Passing Cisco's CCNA and CCNP Exams: The VLAN.DAT File Submitted by Chris on 2006-02-15 and viewed 155 times.

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CCNA and CCNP candidates are often confused about why VLANs and VTP information is still present on a switch after the configuration is erased. Learn why this happens and how to really delete VLAN information in this free tutorial from Chris Bryant, CCIE #12933.

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 see in this abbreviated output 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 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.

Article Source: http://www.awesomewebessentials.com/

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage, home of FREE CCNA & CCNP tutorials. For a FREE copy of my latest e-books, "How To Pass The CCNA" or "How To Pass The CCNP", request one at chris@thebryantadvantage.com!

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