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You can modify the startup configuration through the command interpreter called the EXEC. This chapter provides the following information about using the command interpreter:
This chapter also provides command information about modifying the configuration through two EXEC commands as follows:
Finally, this chapter provides information about how you can review the modifications you have made to the configuration.
The EXEC interprets the commands you enter and carries out the corresponding operations.
You can enter commands when you see the system prompt, which is the system's host name ending with an angle bracket (>). Although the default system host name is Router>, you may have changed this during the initial configuration, or with the hostname configuration command.
The following sections describe how to use the EXEC.
The EXEC accepts commands entered in uppercase letters, lowercase letters, or both. You can also abbreviate commands and other keywords to the number of characters that cause the command to be a unique abbreviation. For example, you can abbreviate the show command to sh.
If you make a typing mistake, you can erase characters one at a time with the Delete or the Backspace key. Press either key to erase the last character entered. To erase the entire line, enter Ctrl-U. (This notation means "Hold down the Ctrl key and press the U key.") In most cases, pressing the Return key after entering a command causes the software to process that command.
You can list available EXEC commands by entering a question mark (?). You can also enter a question mark to obtain more information about commands. For example, enter terminal ? to obtain a list of terminal commands or show ? to obtain a list of show commands.
Certain EXEC commands produce multiple screens of output. At the end of each screen, the EXEC pauses and displays the following:
-More-
Enter a space to continue the output; enter anything else to return to the system command prompt.
For security purposes, the EXEC has two levels of access: user and privileged. The commands available at the user level are a subset of the commands available at the privileged level. Because many of the privileged commands set operating parameters, the privileged level should be password-protected to prevent its unauthorized use. The system prompt for the privileged level ends with a pound sign (#) instead of an angle bracket (>).
The EXEC enable command allows access to the privileged level, prompting for a password if one has been set with the enable-password configuration command. (For more information, see the section "Establishing Passwords and System Security" in the "Configuring the System" chapter of the Router Products Configuration and Reference publication.
Enter the ? (question mark) command at the user level to see a list of the user-level EXEC commands similar to the following:
Router>?connect <host> Connect to host - same as typing just a host namedisconnect <cn> Break the connection specified by name or numberexit, quit Exit from the EXECname-connection Give a connection a logical nameresume Make the named connection be currentshow <cmd> Information commands, type "show ?for listsystat Show terminal lines and userstelnet <host> Connect to host using telnet protocolterminal Change terminal's parameters, type "terminal ?"where Show open connections<cr> To resume connection
Enter enable and enter the password to access the privileged command level. Enter the ? (question mark) command to see a list of privileged-level EXEC commands similar to this example:
Router# ?
clear Reinitialization functions, type "clear ?" for list
configure Configure from terminal or over network
connect <host> Connect to host - same as typing just a host name
debug Enable debugging functions, type "debug ?" for list
disable Turn off privileged commands
disconnect <cn> Break the connection specified by name or number
enable Turn on privileged commands
exit, quit Exit from the EXEC
name-connection Give a connection a logical name
ping Send echo messages
reload Halt and reload system
resume Make the named connection be current
send <line>|* Send message to a terminal line or lines
setup Initialize system configuration
show <cmd> Information commands, type "show ?" for list
systat Show terminal lines and users
telnet <host> Connect to host using telnet protocol
terminal Change terminal's parameters, type "terminal ?"
test Run hardware tests, type "test ?"
trace <address> Trace route to <address>
undebug Disable debugging functions, type "undebug ?"for list
where Show open connections
write Write configuration memory, type "write ?" for list
<cr> To resume connection
To return to the user-level prompt, enter disable at the EXEC prompt.
The setup command facility can be used after first-time startup to make basic changes at any time. The changes you make will affect only the changed elements' current memory values that are stored in nonvolatile memory.
When you enter the setup command facility after first-time startup, you must run through the entire dialog until you come to the element you wish to change. Note that when you use the setup command after first-time startup, the default values indicated within the brackets in the System Configuration Dialog are the values last set using the setup command facility or left as defaults. If you do not want to make the change while still in the System Configuration Dialog, enter Ctrl-C to return to the privileged EXEC prompt.
Refer to the chapter "Preparing for First-Time Startup," for complete descriptions of the values you can assign each item within the dialog.
This section provides a brief overview of using the configure command for advance configuration changes. For detailed information about advanced configuration, refer to the Router Products Configuration and Reference publication.
Use the privileged EXEC command configure to begin advanced configuration of the network server. Begin by entering the privileged level of the EXEC. This is done by entering the enable command at the EXEC prompt:
Router>enable
The EXEC then prompts you for a privileged-level password:
Password:
Enter the password. For security purposes, the password will not be displayed. (Also note that the password is case sensitive.) When you enter the correct password, the system displays the privileged-mode system prompt:
Router#
To begin configuration mode, enter the configure command at the privileged-mode prompt:
Router# configure
When you enter this command, the EXEC prompts you for the source of the configuration subcommands.
Configuring from terminal, memory, or network [terminal]?
The default is to enter commands at the terminal console. Pressing the Return key begins this configuration method. Each configuration technique (terminal, memory, and network) is described in more detail in the chapter, "Miscellaneous System Tasks."
The EXEC provides you with a simple editor for entering the configuration commands, and explains the editing functions. The prompt is as follows:
Enter configuration commands, one per line. Edit with DELETE, CTRL/W, and CTRL/U; end with CTRL/Z
Table 1-1 lists the edit key functions and their meanings.
| Key | Meaning |
|---|---|
| Delete or Backspace | Erases one character. |
| Ctrl-W | Erases a word. |
| Ctrl-U | Erases a line. |
| Ctrl-R | Redisplays a line. |
| Return | Executes single-line commands. |
| Ctrl-Z | Ends configuration mode and returns to the EXEC. |
The configuration subcommands are categorized by these functions:
The descriptions of the commands include the command type and give examples of their use.
As with EXEC commands, you can enter configuration subcommands in uppercase letters, lowercase letters, or both. You can also shorten all commands and other keywords to unique abbreviations. You can add comments by preceding the line with an exclamation point (!). Comments do not affect command processing.
The network server does not display confirmation messages as it executes the commands. If the network server encounters a problem, it displays an error message on the console terminal.
In most cases, you can negate a configuration subcommand or restore a default by typing no before the subcommand keyword. You can usually omit the arguments of the subcommand when you negate it with no. The command descriptions note any exceptions to these rules.
The following examples illustrate how to enter the configuration subcommands.
The EXEC accepts commands in uppercase and lowercase letters. Exclamation points are not parsed and serve as comment lines and delimiters between configuration commands.
Use global configuration commands to enable functions that affect the system rather than a particular line or interface. Global configuration commands can appear any place within the configuration file. An example of this is the global configuration command to define the host name, or the name of the router:
hostname router-1
Commands to enable a particular routing or bridging function are also global configuration commands. The following example illustrates how to enable the Xerox Network System (XNS) routing protocol:
xns routing 0123.4567.abcd
Once enabled, interface characteristics for XNS routing are specified using the interface command and XNS-specific interface subcommands. Command descriptions in the sections describing configuration will define the command type.
Interface subcommands modify the operation of an interface such as an Ethernet, FDDI, or serial port. Interface subcommands always follow an interface command, which defines the interface type.
The following example illustrates how to enable XNS network 1 on interface Ethernet 0:
interface ethernet 0 xns network 1
The following example illustrates how to configure the token rotation timer on interface FDDI 0:
interface FDDI 0 fddi token-rotation-timer 24000
If you forget to enter the interface command, the system displays the message "must specify a network interface."
Line subcommands modify the operation of a serial terminal line. Line subcommands always follow a line command, which defines the line number. If you forget to enter the line command, the system displays the message "must specify a line or range of lines."
The following example illustrates how to set the password on line 5:
line 5 password secretword
Router subcommands are used to configure IP routing protocol characteristics and always follow a router command. The following example illustrates how to set the maximum hop metric for the Cisco IGRP routing protocol:
router igrp metric maximum-hops 150
If you forget to enter the router command, the system displays the message "must specify a routing protocol."
Remember to enter Ctrl-Z to end your configuration sessions, and to use the disable command to leave the privileged mode.
You can review the changes you have made to the configuration and you can display information stored in nonvolatile memory using the EXEC command show configuration. You can use the write terminal command to display the configuration running in memory.
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