CCNA Study Notes1(2)
添加时间: 2007-9-8 2:48:34 作者: Cisco认证考试 阅读次数:59 来源: http://www.d9soft.com
PPP - Point-to-Point Protocol. A successor to SLIP, PPP provides router-to-router and host-to-network connections over synchronous and asynchronous circuits.
DDR - dial-on-demand routing. Technique whereby a Cisco router can automatically initiate and close a circuit-switched session as transmitting stations demand. The router spoofs keep-alives so that end stations treat the session as active. DDR permits routing over ISDN or telephone lines using an external ISDN terminal adaptor or modem.
7. Log into a router in both user and privileged modes.
User EXEC – User mode entered by logging in. Prompt will be Router>. To exit use the logout command.
Privileged EXEC – From user EXEC mode, use the enable EXEC command. Prompt will be Router#. To exit to user EXEC mode use the disable command.
8. Use the context-sensitive help facility.
Entering a question mark (?) at the system prompt displays a list of commands available for each command mode. You can also get a list of any command’s associated keyworkd and arguments with the context-sensitive help feature. To get help specific to a command mode, a command, a keyword, or arguments perform one of the following:
Task Command
Obtain a brief description of the help system in and help
Command mode.
Configure a line or lines to receive help for the full set of full-help
User-level commands when a user types ?.
Configure a line to receive help for the full set of user-level terminal full-help
Commands for this exec session.
Obtain a list of commands that begins with a particular abbreviated-command-entry?
Character string.
Complete a partial command name. abbreviated-command-entry
List all commands available for a particular command mode. ?
List a command’s associated keywords. command ?
List a keyword’s associated arguments. Command keyword ?
9. Use the command history and editing features.
With the current IOS release, the user interface provides a history or record of commands that you have entered. This feature is particularly useful for recalling long or complex command entries including access lists. By default, the system records 10 command lines in its history buffer. To set the number of command lines recorded during the current terminal session use the following command:
terminal history [size number-of-lines]
To configure the number of command lines the system records, complete the following command from line configuration mode:
history [size number-of-lines]
Useful editing commands:
Crtl-P or the up arrow key Recall commands in the history buffer starting with the most recent
command.
Crtl-N or the down arrow Return to more recent commands in the history buffer after recalling
commands with Crtl-P or the up arrow key.
Crtl-B or left arrow key Move the cursor back one character
Crtl-F or right arrow key Move the cursor forward one character
Crtl-A Move the cursor to the beginning of the command line
Crtl-E Move the cursor to the end of the command line
Esc B Move the cursor back one word
Esc F Move the cursor forward one word
Crtl-R or Crtl-L Redisplay the current command line
10. Examine router elements (RAM, ROM, CDP, show).
ROM Read Only, Hard Wired, Boot Strap, IOS, ROM Monitor
RAM IOS & Running Configuration (Main Memory)
NVRAM Startup Config – Saved via battery (10 yr Life Span)
Flash IOS – PCMCIA Cards or SIMMs
Shared RAM Packet Buffering – Not all platforms
The Cisco Discovery Protocol (CDP) is a media- and protocol-independent protocol that runs on all Cisco-manufactured equipment including routers, bridges, access servers and switches. CDP runs on all media that supports Subnetwork Access Protocol (SNAP) including local area network, Frame Relay and ATM media. CDP runs over the data link layer only.
specify the frequency of transmission of CDP updates. cdp timer seconds
specify the amount of time a receiving device should cdp holdtime seconds
hold the information sent by your device before
discarding it.
to disable CDP no cdp run
to disable CDP on an interface no cdp enable
delete the CDP table of information about neighbors clear cdp table
display cdp neighbor information show cdp neighbors [type number] [detail]
The show cdp neighbors command displays: Device ID, interface type and number, hold-time settings, capabilities, platform and port ID information about neighbors. Using the detail option displays the following additional neighbor details: network address, enabled protocols and software version.
11. Manage configuration files from the privileged exec mode.
You can copy a configuration file from a TFTP server to the running configuration or to the startup configuration. When you copy a configuration file to the running configuration, you copy to and run the file from RAM. When you copy a configuration file to the startup configuration, you copy it to the nonvolatile random-access memory (NVRAM).
Step 1 Copy a file from a TFTP server to the router copy tftp running-config
or
Copy tftp startup-config
Step 2 When prompted enter the IP address or domain ip-address or name
name of the server
Step 3 If prompted, enter the filename of the configuration filename
file
Configuration files can also be copied from an rcp server to the local router as well. You must first specify the remote username:
ip rcmd remote-username username
Use steps as above except replace tftp with rcp
to view the configuration in NVRRAM show startup-config
to view the current running configuration show running-config
to re-execute the configuration commands located in NVRAM configure memory
to erase the contents of NVRAM erase startup-config
12. Control router passwords, identification and banner.
Cisco routers have two levels of passwords that can be applied; user and privileged EXEC. The user EXEC passwords are applied to the console, auxiliary and virtual terminal lines of the Cisco router. Password authentication can be either on the line, through a local username definition or a TACACS, extended TACACS, TACACS+ or RADIUS server. To enter privileged EXEC mode, use the enable command. By default, the password will be compared against the password entered with the enable secret global command.
To uniquely identify the router, use the hostname command as follows:
set the hostname hostname name
customize the prompt prompt string
remove the configuration prompt no service prompt config
Banners
banner exec
To display a banner on terminals with an interactive EXEC, use the banner exec global configuration command. This command specifies a message to be displayed when an EXEC process is created (a line is activated, or an incoming connection is made to a VTY line). The no form of this command deletes the EXEC banner.
banner exec d message d
no banner exec
Syntax Description
d Delimiting character of your choice--a pound sign (#) for example. You cannot use the
delimiting character in the banner message.
message Message text.
banner incoming
To specify a banner used when you have an incoming connection to a line from a host on the network, use the banner incoming global configuration command. The no form of this command deletes the incoming connection banner.
banner incoming d message d
no banner incoming
Syntax Description
d Delimiting character of your choice--a pound sign (#) for example. You cannot use the
delimiting character in the banner message.
message Message text.
An incoming connection is one initiated from the network side of the router. Incoming connections are also called reverse Telnet sessions. These sessions can display MOTD banners and INCOMING banners, but they do not display EXEC banners. Use the no motd-banner line configuration command to disable the MOTD banner for reverse Telnet sessions on asynchronous lines. When a user connects to the router, the MOTD banner appears before the login prompt. After the user successfully logs in to the router, the EXEC banner or INCOMING banner will be displayed, depending on the type of connection. For a reverse Telnet login, the INCOMING banner will be displayed. For all other connections, the router will display the EXEC banner. Incoming banners cannot be suppressed. If you do not want the incoming banner to appear, you must delete it with the no banner incoming command.
13. Identify the main Cisco IOS commands for router startup.
14. Check an initial configuration using the setup command.
The command parser (Command Line Interface - CLI) allows you to make very detailed changes to your configurations. However, some major configuration changes do not require the granularity provided by the command parser. In these cases, you can use the setup command facility to make major enhancements to your configurations. For example, you might want to use setup to add a protocol suite, to make major addressing scheme changes, or to configure a newly installed interface. Although you can use the command parser to make these major changes, the setup command facility provides you with a high-level view of the configuration and guides you through the configuration change process.
Additionally, if you are not familiar with Cisco products and the command parser, the setup command facility is a particularly valuable tool because it asks you the questions required to make configuration changes.
Note: If you use setup to modify a configuration because you have added or modified the hardware, be sure to verify the physical connections using the show version command. Also, verify the logical port assignments using the show running-config command to ensure that you configure the proper port.
To enter the setup command facility, enter ‘setup’ in privileged EXEC mode:
When you enter the setup command facility after first-time startup, an interactive dialog called the System Configuration Dialog appears on the system console screen. The System Configuration Dialog guides you through the configuration process. It prompts you first for global parameters and then for interface parameters. The values shown in brackets next to each prompt are the default values last set using either the setup command facility or the configure command. The prompts and the order in which they appear on the screen vary depending on the platform and the interfaces installed in the device.
You must run through the entire System Configuration Dialog until you come to the item that you intend to change. To accept default settings for items that you do not want to change, press the Return key.
To return to the privileged EXEC prompt without making changes and without running through the entire System Configuration Dialog, press Ctrl-C.
The facility also provides help text for each prompt. To access help text, press the question mark (?) key at a prompt.
When you complete your changes, the setup command facility shows you the configuration command script that was created during the setup session. It also asks you if you want to use this configuration. If you answer Yes, the configuration is saved to NVRAM. If you answer No, the configuration is not saved and the process begins again. There is no default for this prompt; you must answer either Yes or No.
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