How to reset the Cisco Catalyst 2950, step by step?

#write erase

(which is deleting the configuration file)

#reload

then,

#delete flash:vlan.dat

(which is deleting the vlan database file)

#reload

example from commande:

Switch>enable
Switch#delete flash:vlan.dat
Delete filename [vlan.dat]? vlan.dat
Delete flash:vlan.dat? [confirm]y
Switch#

wen not working

older versions

https://community.cisco.com/t5/other-network-architecture-subjects/deleting-vlan-database/td-p/501648