Reset to factory default: Extreme Networks Summit, Cisco Ctalist 2960, Ericsson ECN330

Returning the switch to the default configuration results in the loss of all existing configurations. It can be dangerous in you network or very useful when you buy used equipment in eBay ;)

Extreme Networks Summit
To return the switch configuration to factory defaults¹, use the following command:

unconfig switch

This command resets the entrie configuration except user accounts and passwords. To reset all parameters, use the following command:

unconfig switch all

In case that you haven't access to the switch, connect to Summit by console cable, power cycle the switch and immediatly press and hold space button while command prompt appear²

BootRom >

Than use the following command

config none
reboot

Cisco Catalist 2960
Connect to switch’s console, than power off the switch. Reconnect the power cord to the switch and, within 15 seconds, press the "Mode" button while the System LED is still flashing green. Continue pressing the "Mode" button until the System LED turns briefly amber and then solid green; then release the "Mode" button³.
Question Would you like to reset the system back to the default configuration (y/n)? will appear in console, press y. Finally, reboot the switch by reload command.

Ericsson ECN330
Make a direct connection to the switch’s console port and power cycle the switch. Immediately after powering on, press CTRL+U and type the password mercury to access the system file menu⁴. Select D delete all user-defined configuration files. Press Q to boot the ECN330.

References:

¹ Summit Switch Installation and User Guide
² Resetting the Extreme Networks switches (russian)
³ Catalyst 2960 Switch Software Configuration Guide, 12.2(25)SEE
⁴ ECN330 Installation Guide