How to Reset a Cisco Catalyst 3550 / 3560 Switch to Factory Defaults
Enter the following commands in the privileged mode: (# prompt)
Delete filename [vlan.dat]?
Delete flash:vlan.dat? [confirm]
Erasing the nvram filesystem will remove all configuration files! Continue? [con
Erase of nvram: complete
00:04:46: %SYS-7-NV_BLOCK_INIT: Initialized the geometry of nvram
If you are prompted to save anything before reloading, respond by saying no.
After the switch reloads you should get the initial config prompt.