Note:

'//' means comments
'>' means in user EXEC mode
'# means in privileged EXEC mode

To bypass password-prompting at the init stage
// unplug power supply
// hold down the 'mode' button on the left of panel while reconnecting the power cord.
// release the 'mode' button after the LED above 1x is no longer illuminated.
>flash_init
>load_helper
>dir flash:
>rename flash:config.text flash:config.old (so that there no copy to read when the system start)
>boot
// wait
'Continue with the configuration dialog?[yes/no]:
>N
>en
>type rename flash:config.old flash:config.text( make sure cannot backspace cause backspace also consider as a word)
>copy flash:config.text system:running-config

To upgrade enhanced verions of IOS (from SMI to EMI)
>boot system flash:c3550-i5q3l2-mz.121-9.EA1c.bin ( to boot the new image from flash)
>end
>reload (wait)

To assign IP address to switch (manually)
# conf t
# int vlan1
# ip address 10.10.10.1 255.0.0.0
# end
# write mem
# show run(to see configuration)

To copy file from tftp server
// First need to have a valid ip addess for the tftp server
// Then start your tftp server
# copy flash:c3550-i5q3l2-mz.121-9.EA1c.bin tftp:/10.10.10.100

To create password for privilege mode
# conf t
# enable password derrick ( password means the word can be seem when show run)
# enable secret derrick2 (secret means the word is encryted when show run)
# end

To remove password
# conf t
# no enable password(if in password mode)
# no enable secret (if in secret mode)
# end

To create user and password for switch and telnet
# conf t
# username derrick privilege 15 password 0
# line console 0 (for inital login on the console port) or line vty 0 15 (allowing for up to 16 telnet sessions at one time)
#login local
# password cisco
# end
# show run (check for password)

To create vlan
# conf t
#vlan 10
# end

To assign ip address to vlan
# conf t
# int vlan10
# ip address 10.10.10.2 255.255.255.0 ( note: each vlan cannot have two same ip addresses )
# exit
# show int vlan10 (to check)

To assign port to vlan
# conf t
# int fa0/1
# switchport mode access
# switchport access vlan 10
# end
# show int fa0/1 switchport(to check)

To create etherchannel
# conf t
# int port-channel 2
# int range fa0/21-24
# switchport trunk encapsulation dot1q
# channel-group group 2 mode on
# end
# show etherchannel summary( to show summary)
# no int port-channel 1(to remove other port channel)

To set portfast
# conf t
# int fa0/1
# spanning-tree portfast
# end
# show run

To see mac address of machines connected
# sh arp

To see what vlans connected
# sh ip route

To see rip database
# sh ip rip database