Cisco IOS Configuration Commands and Security Settings

Cisco Device Access and Security Passwords

• Console Password: Provides limited access for devices via the console connection.
• Enable Password: Restricts access to the privileged EXEC mode.
• Enable Secret Password: An encrypted password restricting access to the privileged EXEC mode.
• VTY Password: Limits access to devices using Telnet.

Basic Configuration Command Examples

Console Access Configuration

Switch(config)# line console 0
Switch(config-line)# password password
Switch(config-line)# login

Virtual Terminal (VTY) Access

Router(config)# line vty 0 4
Router(config-line)# password password
Router(config-line)# login

Banner Message of the Day

Switch(config)# banner motd # message #

Interface IP Address Assignment

Router(config)# interface FastEthernet 0/0
Router(config-if)# ip address ip_address netmask
Router(config-if)# no shutdown

ICMP Response Indicators

• ! - Indicates the receipt of an ICMP echo reply.
• . - Indicates a time limit expired while waiting for a reply.
• U - Indicates that an ICMP unreachable message was received.

Cisco IOS Command Reference by Mode

Privileged EXEC Mode Commands

• copy running-config startup-config - Copy the active configuration to NVRAM.
• copy running-config startup-config - Copy the configuration in NVRAM to RAM.
• erase startup-configuration - Clear the configuration stored in NVRAM.
• ping ip_address - Send an ICMP echo request to the specified address.
• traceroute ip_address - Track every hop to the destination address.
• show interfaces - Show statistics for all interfaces of a device.
• show clock - Show the current time set in the router.
• show version - Display the currently loaded IOS version, hardware, and device information.
• show arp - Show the ARP table of the device.
• show startup-config - Display the configuration stored in NVRAM.
• show running-config - Show the contents of the configuration file currently running in RAM.
• show ip interface - Display IP statistics for the interfaces of a router.
• configure terminal - Enter global configuration mode.

Terminal Configuration Mode Commands

• hostname hostname - Assign a host name to the device.
• enable password password - Set an unencrypted password to enable privileged mode.
• enable secret password - Set a securely encrypted password to enable privileged mode.
• service password-encryption - Encrypt the display of all passwords except the secret.
• banner motd # message # - Set a title with the message of the day.
• line console 0 - Enter the console line configuration mode.
• line vty 0 4 - Enter the virtual terminal (Telnet) line configuration mode.
• interface INTERFACE_NAME - Enter interface configuration mode.

Line Configuration Mode Commands

• login - Enable password checking at login.
• password password - Set the password for the line.

Interface Configuration Mode Commands

• ip address ip_address netmask - Set the interface IP address and subnet mask.
• description description - Set a descriptive label for the interface.
• clock rate value - Set the clock frequency for the DCE device.
• no shutdown - Administratively activate the interface.
• shutdown - Administratively deactivate the interface.