How to secure cisco router or a switch with passwords

To configure the console password

Router>enable

Router#configure terminal

Router(config)# line console 0
Router(config-line)# password f5skills
Router(config-line)# login
Router(config-line#Ctrl-Z
Router#

To configure the auxilary password

Router>enable
Router#config t

Router(config)#line aux 0
Router(config-line)#password f5skills
Router(config-line)#login
Router(config-line)# Ctrl-Z
Router#

To password protect VTY Ports (Telnet Ports)

Configuring the VTY password is very similar to doing the Console and Aux ones. The only difference is that there are 5 VTY virtual ports, which are named 0, 1, 2, 3, and 4. You can use the shortcut 0 4 (a zero, a space, and 4) to set all 5 passwords at the same time. To configure the VTY password, follow these steps.

Router#config t
Router(config)#line vty 0 4
Router(config-line)#password f5skills
Router(config-line)#login
Router(config-line)# Ctrl-Z
Router#

To password protect Privileged Mode

The Enable Password is the old form of the password for "Privileged Mode". Here the password is stored un-encrypted.

Router#config t
Router(config)#enable password f5skills
Router(config-line)# Ctrl-Z
Router#

Enable Secret provides better security since password is kept encrypted using irreversible encryption algorithm.

Router#config t
Router(config)#enable secret f5skills
Router(config-line)# Ctrl-Z
Router#