Erase IOS configuration files delete flash:vlan.dat delete vlan information, you will have to confirm write erase erase the IOS configuration reload reboot the IOS
[...]
Activate layer 3 functions on Cisco Catalyst 2960 series switch Requirement: at least Cisco IOS Software Release 12.2(55) lanbase firmware edition is needed
[...]
EtherChannel setup conf t enter into configuration mode int range fa0/1-2 channel-group 1 mode active enable EtherChannel with LACP open protocol. It has
[...]
Spanning tree show spanning-tree list spanning tree information conf t enter into configuration mode spanning-tree vlan 1 root primary turn the switch primary
[...]
Setup trunk between switches conf t enter into configuration mode of switch #1 int fa0/24 select interface for using trunking switchport mode trunk
[...]
Enable telnet access trough interface VLAN conf t enter into configuration mode enable secret somepassword set password for administration mode level line vty 0
[...]
Create interface VLAN conf t enter into configuration mode interface vlan 4 enter into interface vlan configuration mode. An existing VLAN needs to
[...]