Cisco IOS Command Summary—Four Modes to Access and Configure a Cisco Router
The four modes for accessing and configuring a Cisco router are: user EXEC mode, privileged EXEC mode, global configuration mode, interface configuration mode
Each mode has a unique command set.
Purpose of each Mode
user EXEC mode is the initial startup mode. A router configuration session can be initiated using terminal emulation programs such as Kermit, HyperTerminal, or telnet.
privileged EXEC mode is the system administrator mode. In this mode configuration files can be read, the router can be rebooted, and operating parameters can be changed.
global configuration mode is used to modify system-wide configuration parameters, such as routing tables and routing algorithms.
interface configuration mode is used to modify the Ethernet and serial port configurations.
How to Change Modes
user Exec mode is entered by starting a terminal emulation program, such as kermit or HyperTerminal, or by starting a telnet session. The workstation must physically be connected to the console port on the router by either a rollover cable (kermit or HyperTerminal) or to an Ethernet port by a standard patch cable (telnet). See Figure 1 for port locations. Typically a password must be entered to establish the connection. The user Exec mode prompt has the following form: RouterName>
privileged Exec mode is entered from user Exec mode by typing enable. A password must be supplied to complete the connection. The privileged Exec mode prompt has the following form: RouterName#
global configuration mode is entered from privileged Exec mode by typing configure terminal or config t. No password is required. The global configuration mode prompt has the following form: RouterName (config)#
interface configuration mode is entered from global configuration mode by typing interface InterfaceName, where the InterfaceName is either Ethernet0, Serial0, or Serial1. The interface configuration mode prompt has the following form: RouterName(config-if)#
- To exit interface configuration mode type exit. This will return the system to global configuration mode.
- To exit global configuration mode type exit. This will return the system to privileged Exec mode.
- To exit global configuration mode type disable. This will return the system to user Exec mode.
- To exit user Exec mode type logout. This will end the session.
Alternatives to Exit Options
- To return to privileged Exec mode directly from any configuration mode type end.
- Typing logout or exit from privileged Exec mode will also end the session.
How to get Command Help
Typing ? will display a list of commands for that mode. Typing part of a command followed by a ? will display additional information about that command.
Selected Privileged Exec Mode Commands
show running-config – displays current router configuration for the router
show startup-config – displays the startup configuration for the router
reload - restarts the router. Discards running configuration and reloads startup configuration
copy running-config startup-config - saves the current configuration to NVRAM. The new configuration takes effect after the router is rebooted.
show ip route – displays the contents of the routing table
clear ip route – deletes all routing table entries
show interfaces – displays information about all network interfaces
Selected Global Configuration Commands
ip routing – enables IP forwarding
no ip routing – disables IP forwarding and deletes content of routing table
ip route-cache – enables route caching (default mode)
no ip route-cache – disables route caching
ip route ipDestinationAddr subnetmask gw_address – adds a static route to the routing table. gw_address is the IP address of the default gateway (next hop router)
ip route ipDestinationAddr subnetmask Interface – similar to above, but Interface is the network interface name
no ip route ipDestinationAddr subnetmask gw_address – deletes route table entry
no ip route ipDestinationAddr subnetmask Interface – deletes route table entry
Examples – Global Configuration Commands
ip route 10.21.0.0 255.255.0.0 10.11.1.4 – this command adds a route to the routing table for network 10.21.0.0 with subnet mask 255.255.0.0. 10.11.1.4 is the default gateway (next hop router) address.
ip route 0.0.0.0 0.0.0.0 10.0.4.4 – this command adds 10.0.4.4 as a default gateway
Selected Interface Configuration Mode Commands
no shutdown – enables network interface
shutdown – disables network interface
ip address IPaddress netmask – Sets the IP address and subnet mask for an interface
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