CCNA :) Be a Good Network Administrator

Configuring an interface description 3.2.3 This page will teach students how to configure an interface description. To configure an interface description, enter global configuration mode. From global configuration mode, enter interface configuration mode. Use the command description followed by the information. The steps to configure an interface description are as follows: 1. Use the configure terminal command to enter global configuration mode. 2. Enter a specific interface mode such as interface ethernet 0. 3. Enter the command description followed by the information that is to be displayed, such as XYZ Network, Building 18. 4. Use Ctrl-Z to exit interface mode and return to privileged EXEC mode. 5. Use the copy running-config startup-config command to save the configuration changes to NVRAM. Here are two examples of interface descriptions: interface ethernet 0 description LAN Engineering, Bldg.2 interface serial 0 description ABC network 1, Circuit 1 The next p...

Interface descriptions 3.2.2 This page will explain what interface descriptions are and why they are used. An interface description should identify important information such as a router, a circuit number, or a specific network segment. A description of an interface can help a network user remember specific information about the interface, such as what network the interface services. The description will appear in the configuration files that exist in the router memory. However, it will not affect the operation of a router. A description only provides information about an interface. Descriptions are created by following a standard format that applies to each interface. The description may include the purpose and location of the interface, other devices or locations connected to the interface, and circuit identifiers. Descriptions allow support personnel to better understand the scope of problems related to an interface and allow for faster resolution of problems. The next page ...

Importance of configuration standards 3.2.1 This page explains why it is important to develop standards for configuration files within an organization. Configuration standards can be used to control of the number of configuration files that must be maintained, how the files are stored, and where the files are stored. A standard is a set of rules or procedures that are either widely used or officially specified. If an organization does not have standards, the network will be in chaos if a service interruption occurs. Network management requires a centralized support standard. Configuration, security, performance, and other issues must be addressed for the network to function properly. The creation of standards for network consistency helps reduce network complexity, unplanned downtime, and events that may affect network performance. The next page will discuss interface descriptions.

Configuring an Ethernet interface 3.1.7 This page will explain how an Ethernet interface can be configured from the console or a virtual terminal line. Each Ethernet interface must have an IP address and subnet mask to route IP packets. To configure an Ethernet interface follow these steps: 1. Enter global configuration mode. 2. Enter interface configuration mode. 3. Specify the interface address and subnet mask. 4. Enable the interface. By default, interfaces are turned off, or disabled. To turn on or enable an interface, the command no shutdown is entered. If an interface needs to be disabled for maintenance or troubleshooting, use the shutdown command to turn off the interface. This page concludes this lesson. The next lesson will explain how a configuration is finalized. The first page covers the importance of configuration standards.

Co

Making configuration changes 3.1.6 This page will explain how configuration variables can be changed in different modes. If a configuration requires modification, go to the appropriate mode and enter the proper command. For example, if an interface must be enabled, enter global configuration mode, enter interface mode, and issue the command no shutdown. To verify changes, use the show running-config command. This command will display the current configuration. If the variables displayed are not correct, the environment can be changed in the following ways: • Issue the no form of a configuration command. • Reload the system to return to the original configuration file from NVRAM. • Copy an archived configuration file from a TFTP server. • Remove the startup configuration file with the erase startup-config, then restart the router and enter setup mode. To save the configuration variables to the startup configuration file in NVRAM, enter the following command at the privilege...

Configuring a serial interface 3.1.5 This page will explain how a serial interface can be configured from the console or through a virtual terminal line. To configure a serial interface follow these steps: 1. Enter global configuration mode. 2. Enter interface mode. 3. Specify the interface address and subnet mask. 4. Set clock rate if a DCE cable is connected. Skip this step if a DTE cable is connected. 5. Turn on the interface. Each connected serial interface must have an IP address and subnet mask to route IP packets. Configure the IP address with the following commands: Router(config)#interface serial 0/0 Router(config-if)#ip address Serial interfaces require a clock signal to control the timing of the communications. In most environments, a DCE device such as a CSU/DSU will provide the clock. By default, Cisco routers are DTE devices but they can be configured as DCE devices. On serial links that are directly interconnected, as in a lab environment, one side must...

Examining the show commands 3.1.4 This page will introduce some show commands. Many of these commands can be used to examine the contents of files in the router and for troubleshooting. In both privileged EXEC and user EXEC modes, the command show ? provides a list of available show commands. The list is considerably longer in privileged EXEC mode than it is in user EXEC mode. Students should learn the functions of the following commands: • show interfaces – Displays statistics for all interfaces on a router. To view the statistics for a specific interface, enter the show interfaces command followed by the specific interface slot/port number. This is shown in the following example: Router#show interfaces serial 0/1 • show controllers serial - Displays information that is specific to the interface hardware. This command must also include the port or slot/port number of the serial interface. For example: Router#show controllers serial 0/1 • show clock - Shows the time set i...

Configuring router passwords 3.1.3 This page will explain how router passwords are configured and why they are important. Passwords restrict access to routers. Passwords should always be configured for virtual terminal (vty) lines and the console line. Passwords are also used to control access to privileged EXEC mode so that only authorized users may make changes to the configuration file. The following commands are used to set an optional but recommended password on the console line: Router(config)#line console 0 Router(config-line)#login Router(config-line)#password A password must be set on one or more of the vty lines for users to gain remote access to a router through Telnet. Most Cisco routers support five vty lines numbered 0 through 4. Other hardware platforms support different numbers of vty connections. The same password is generally used for all vty lines. However, a unique password can be set for one line to provide a fall-back entry to the router if the other...

Configuring a router name 3.1.2 This page will explain how a router name is configured. A router should be given a unique name as one of the first configuration tasks. This task is accomplished in global configuration mode with the following command: Router(config)#hostname Tokyo Tokyo(config)# When the Enter key is pressed, the prompt will change from the default host name, which is Router, to the newly configured host name, which is Tokyo. The next page will show students how to configure router passwords.

Configuring a router name 3.1.2 This page will explain how a router name is configured. A router should be given a unique name as one of the first configuration tasks. This task is accomplished in global configuration mode with the following command: Router(config)#hostname Tokyo Tokyo(config)# When the Enter key is pressed, the prompt will change from the default host name, which is Router, to the newly configured host name, which is Tokyo. Configuring router passwords 3.1.3

CLI command modes 3.1.1 This page will discuss some features that are available from global configuration mode. All CLI configuration changes to a Cisco router are made from global configuration mode, which is sometimes called global config. Global config is the primary configuration mode. Specific modes are used for various configuration changes, but these modes are all subsets of the global configuration mode. Global configuration mode commands are used in a router to apply configuration statements that affect the system as a whole. The following command moves the router into global configuration mode and allows entry of commands from the terminal: Note: The prompt changes to indicate that the router is now in global configuration mode. Router#configure terminal Router(config)# The prompt will change to indicate that the router is in global configuration mode. Here are a few of the modes that can be entered from global configuration mode: • Interface mode • Line m...

Overview The initial steps that are used to configure a router are not very difficult. If students become familiar with these steps and learn how to move between the router user modes, it will be easier to perform complex router configurations. This module introduces the basic configuration modes of the router and provides opportunities to practice simple configurations. A clear, easy to understand router configuration that is backed up regularly should be a goal of all network administrators. The Cisco IOS provides many tools that an administrator can use to add information to the configuration file for documentation purposes. A network administrator should provide as much information as possible in case another person becomes responsible for the network. This module covers some of the objectives for the CCNA 640-801, INTRO 640-821, and ICND 640-811 exams. - Students who complete this module should be able to perform the following tasks: • Name a router • Set passwords • E...

Summary This page summarizes the topics discussed in this module. The Cisco IOS is embedded in all Cisco routers. The purpose of the Cisco IOS software is to provide basic routing and switching functions, to give the network scalability, and to provide a reliable and secure way to access the network resources. The Cisco IOS software uses a command-line interface accessed through a console session or by using a dial-up connection through a modem connected to the router AUX port. A Telnet session to the router can be established remotely if at least one interface is configured with an IP address. Cisco IOS software provides a command interpreter service known as the command EXEC. After each command is entered, the EXEC validates and executes the command. There are two access levels available for added security. The user EXEC mode, which is identified by a > prompt, provides basic monitoring commands. From user EXEC mode, a user can run basic commands. For example, the user c...

The show version command 2.2.10 This page will discuss the show version command. This command displays information about the Cisco IOS software version that is installed on the router. This includes the configuration register and the boot field settings. Figure shows the following information from the show version command: • IOS version and descriptive information • Bootstrap ROM version • Boot ROM version • Router up time • Last restart method • System image file and location • Router platform • Configuration register setting Use the show version command to identify a router IOS image and boot source. This page concludes the lesson on basic router commands. The next page will summarize the main points from this module.

Troubleshooting command line errors 2.2.9 This page will show students how to locate and fix command line errors. Command line errors occur primarily from typing mistakes. If a command keyword is incorrectly typed, the user interface uses the caret symbol (^) to identify and isolate the error. The ^ appears at the point in the command string where an incorrect command, keyword, or argument was entered. The error location indicator and interactive help system allow the user to easily find and correct syntax errors. Router#clock set 13:32:00 23 February 99 ^ % Invalid input detected at '^' marker. The caret symbol (^) and help response indicate an error at 99. To list the correct syntax, enter the command up to the point where the error occurred and then enter a question mark (?): Router#clock set 13:32:00 23 February ? <1993-2035> Year Router#clock set 13:32:00 23 February Use the correct syntax to add the year and press Enter or Return to execute the...

Router command history 2.2.8 The user interface provides a history or record of commands that have been entered. This page will explain the use and benefits of this feature. This feature is particularly useful for recalling long or complex commands or entries. The command history feature can be used to perform the following tasks: • Set the command history buffer size • Recall commands • Disable the command history feature The command history is enabled by default and the system records ten command lines in its history buffer. To change the number of command lines the system records during a terminal session, use the terminal history size or the history size command. The maximum number of commands is 256. To recall the most recent command in the history buffer, press Ctrl-P or the Up Arrow key. Repeat this process to recall successively older commands. To return to a more recent command in the history buffer, press Ctrl-N or the Down Arrow key. Repeat this process to recall s...

Enhanced editing commands  2.2.7 This page will introduce the enhanced editing mode that is available in the Cisco IOS user interface. This mode provides a set of editing key functions that allows a user to edit a command line as it is being typed. The key sequences indicated in Figure can be used to move the cursor on the command line for corrections or changes. Although enhanced editing mode is automatically enabled with the current software release, it can be disabled if it interferes with the interaction of written scripts. To disable enhanced editing mode, type terminal no editing at the privileged EXEC mode prompt. The editing command set provides a horizontal scrolling feature for commands that extend beyond a single line on the screen. When the cursor reaches the right margin, the command line shifts ten spaces to the left. The first ten characters of the line cannot be seen, but a user can scroll back and check the syntax at the beginning of the command. To scroll ba...

Keyboard help in the router CLI 2.2.6 This page will introduce some router help functions. A question mark, ?, can be entered at the user EXEC or privileged EXEC mode prompt to display a list of available commands. Notice the --More-- at the bottom of the display in Figure . The --More-- prompt indicates that there are multiple screens of output. When a --More-- prompt appears, press the Spacebar to view the next available screen. To display just the next line, press the Return or Enter key. Press any other key to return to the prompt. To access privileged EXEC mode, type enable or the abbreviation en or ena. This might cause the router to prompt the user for a password if one has been set. Figure lists the commands that are available in privileged EXEC mode. Screen output varies, depending on Cisco IOS software level and router configuration. The help function, or question mark, ?, can be used to display the commands that are used to perform certain tasks. The following exer...

Router login 2.2.5 To enter commands and configure a Cisco router, a user must log into the router to access the user interface. This page will show students how to log into a router. For security purposes, a Cisco router has two levels of access to commands: • User EXEC mode – Typical tasks include commands that check the status of a router. • Privileged EXEC mode –Typical tasks include commands that change the router configuration. The user EXEC mode prompt is displayed upon login to a router, as shown in Figure . To enter privileged EXEC mode, type enable at the > prompt. If a password has been set, enter it at the password: prompt. The two commands that can be used to set a password for privileged EXEC mode are enable password and enable secret. Two commands can be used to set a password used to access privileged EXEC mode: enable password and enable secret. If both commands are used, the enable secret command takes precedence. After the login steps have been complete...

Establish a console session 2.2.4 This page will explain how a console session is established with a router. All Cisco routers include a TIA/EIA-232 asynchronous serial console port. The console port is an RJ-45. Cables and adapters are needed to connect a console terminal to the console port. A console terminal is an ASCII terminal or PC that runs terminal-emulation software such as HyperTerminal. Use an RJ-45 to RJ-45 rollover cable with a female RJ-45 to DB-9 adapter to connect this type of a PC to the console port. The default parameters for the console port are 9600 baud, 8 data bits, no parity, 1 stop bit, and no flow control. The console port does not support hardware flow control. Take the following steps to connect a terminal to the console port on a router: 1. Connect the terminal using the RJ-45 to RJ-45 rollover cable and an RJ-45 to DB-9 adapter. 2. Configure the terminal or PC terminal emulation software for 9600 baud, 8 data bits, no parity, 1 stop bit, and n...

Router LED indicators 2.2.2 This page will explain how routers use LED indicators. Cisco routers use LED indicators to provide status information. LED indicators will vary for different Cisco router models. An interface LED indicates the activity of the corresponding interface. A problem may be indicated if an LED is off when the interface is active and the interface is correctly connected. If an interface is extremely busy, its LED will always be on. The green OK LED to the right of the AUX port will be on after the system initializes correctly. The next page will examine the initial router bootup The initial router bootup 2.2.3 This page will discuss the information and messages that are displayed during the initial router bootup. This information will vary, depending on the interfaces in the router and the Cisco IOS release. The screens displayed on this page are for reference only and may not reflect what the screen displays on the console. In Figure , the statement “...

Initial startup of Cisco routers 2.2.1 This page will explain the startup process for Cisco routers. A router initializes by loading the bootstrap, the operating system, and a configuration file. If the router cannot find a configuration file, it enters setup mode. Upon completion of the setup mode, a backup copy of the configuration file may be saved to NVRAM. The goal of the startup routines for Cisco IOS software is to start the router operations. To do this, the startup routines must accomplish the following: • Verify that the router hardware is tested and functional. • Find and load the Cisco IOS software. • Find and apply the startup configuration file or enter the setup mode. When a Cisco router powers up, it performs a power-on self test (POST). During this self test, the router executes diagnostics from ROM on all hardware modules. These diagnostics verify the basic operation of the CPU, memory, and network interface ports. After verifying the hardware functions,...

Operation of Cisco IOS software 2.1.5 This page will introduce the three distinct operating environments, or modes, of Cisco IOS devices: The Cisco IOS devices have three distinct operating environments or modes: • ROM monitor • Boot ROM • Cisco IOS At startup, a Cisco router normally loads into RAM and executes one of these operating environments. A system administrator can use the configuration register setting to control the default startup mode for a router. The ROM monitor performs the bootstrap process and provides low-level functionality and diagnostics. It is used to recover from system failures and to recover a lost password. The ROM monitor cannot be accessed through any of the network interfaces. It can only be accessed by way of a direct, physical connection through the console port. When the router is running in boot ROM mode, only a limited subset of the Cisco IOS feature set is available. Boot ROM allows write operations to flash memory and is used primar...

Cisco IOS software features 2.1.4 This page will introduce some IOS images that are provided by Cisco for devices that span a wide range of network product platforms. Cisco continues to develop different IOS software images to optimize the Cisco IOS software that these various platforms require. Each image represents a different feature set that serves the various device platforms, available memory resources, and customer needs. Although there are numerous IOS images for different Cisco device models and feature sets, the basic configuration command structure is the same. The configuration and troubleshooting skills that are acquired for any device will apply to a wide range of products. The naming convention for the different Cisco IOS releases contains three parts: • The platform on which the image runs • The special features supported in the image • Where the image runs and whether it has been zipped or compressed One of the main considerations when selecting a new IOS...

Router user interface modes 2.1.3 This page will introduce two user interface modes that can be configured for Cisco IOS. The Cisco CLI uses a hierarchical structure. This structure requires entry into different modes to accomplish particular tasks. For example, to configure a router interface, the user must enter interface configuration mode. All configurations that are entered in interface configuration mode apply only to that interface. Each configuration mode is indicated with a distinctive prompt and allows only commands that are appropriate for that mode. The IOS provides a command interpreter service known as the command executive (EXEC). After each command is entered, the EXEC validates and executes the command. As a security feature the Cisco IOS software separates the EXEC sessions into two access levels. These levels are user EXEC mode and privileged EXEC mode. The privileged EXEC mode is also known as enable mode. The following are the features of the user EXEC mode...

Router user interface 2.1.2 This page will review the Cisco IOS. The IOS is a core technology that extends across most of the Cisco product line. Its operation details may vary on different internetworking devices. The CLI environment can be accessed several ways. Typically, the CLI is accessed through a console session. A console uses a low speed serial connection directly from a computer or terminal to the console connection on the router. A CLI session can also be accessed remotely through a dialup connection using a modem connected to the router AUX port. Neither of these methods require that the router have any IP services configured. A third method of accessing a CLI session is to Telnet to the router. To establish a Telnet session to the router, at least one interface must be configured with an IP address, and virtual terminal sessions must be configured for login and passwords. The next page discusses the different user modes that are available for Cisco IOS.

Module 2: Introduction to Routers Overview : Cisco technology is based on the Cisco IOS, which is the software that controls the routing and switching functions of network devices. A solid understanding of the IOS is essential for a network administrator. This module will introduce the main features of the IOS and will provide practice in working with the IOS. All network configuration tasks, from the most basic to the most complex, require a strong foundation in the basics of router configuration. This module will provide the tools and techniques for basic router configuration that will be used throughout this course. This module covers some of the objectives for the CCNA 640-801, INTRO 640-821, and ICND 640-811 exams. - Students who complete this module should be able to perform the following tasks: • Describe the purpose of the IOS • Describe the basic operation of the IOS • Identify various IOS features • Identify the methods to establish a command-line interface (CLI) s...