Cisco IOS Commands to Know (and other stuff)

Random Commands
router# show ip int bri      // show ip interfaces (brief version)
router# era sta              // "erase startup" configuration
router# show ver             // "show version" of operating system, etc


Assign IP Address:
router# int fa0/0
router# ip address 192.168.1.1 255.255.255.0
router# no shutdown          // enable interface


Run a command from any IOS level:
router# do show ip int bri   // the magic command is "do"


Write Router Commands
// copy running-config (in RAM) to the startup-config (in NVRAM (Non-Volatile RAM) so it works after reboot or crash
Router# copy running-config startup-config    // (copy run start)
OR 
router# write                // "wr" for short


Backup Router running-config to TFTP server:
router# copy run tftp        // copy "what" "where"
// all you need to know is the IP address


Erase Configuration to load new configuration:
router# erase startup


Restore NVRAM after erase startup:
router# reload


Restore Router running-config from TFTP server:
// first you must reconfigure the IP address for the router
router# copy tftp run        // copy "where" "what"


Erase Operating System from Router
router# copy flash tftp      // backup OS
// enter the filename of the OS (usually *.bin)


Restore OS to Router
router# copy tftp flash      // will be the same *.bin that you backed up