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 primarily to replace the Cisco IOS image that is stored in flash. The Cisco IOS image can be modified in boot ROM with the copy tftp flash command. This command copies an IOS image that is stored on a TFTP server into the flash memory of a router.
The normal operation of a router requires use of the full Cisco IOS image as stored in flash. In some devices, the IOS is executed directly from flash. However, most Cisco routers require a copy of the IOS to be loaded into RAM and also executed from RAM. Some IOS images are stored in flash in a compressed format and have to be expanded when copied to RAM.
To see the IOS image and version that is running, use the show version command, which also indicates the configuration register setting. The show flash command is used to verify that the system has sufficient memory to load a new Cisco IOS image.
This page concludes the discussion about Cisco IOS. The next lesson will describe the initial startup of Cisco routers.
Sunday, May 2, 2010
Cisco IOS software features
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 image is compatibility with the router flash and RAM memory. In general, the newer the release and the more features that it provides, the more flash and RAM memory it requires. Use the show version command on the Cisco device to check the current image and available flash.
The Cisco support site has tools available to help determine the amount of flash and RAM required for each image. For example, specific IOS features can be selected using the Cisco Software Advisor, which is available to registered Cisco.com users. The Cisco Software Advisor is an interactive tool that provides the most current information and allows users to select options that meet network requirements.
Before installing a new Cisco IOS software image on the router, check to see if the router meets the RAM memory and flash requirements for that image. To see the amount of RAM, issue the show version command:
…
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 image is compatibility with the router flash and RAM memory. In general, the newer the release and the more features that it provides, the more flash and RAM memory it requires. Use the show version command on the Cisco device to check the current image and available flash.
The Cisco support site has tools available to help determine the amount of flash and RAM required for each image. For example, specific IOS features can be selected using the Cisco Software Advisor, which is available to registered Cisco.com users. The Cisco Software Advisor is an interactive tool that provides the most current information and allows users to select options that meet network requirements.
Before installing a new Cisco IOS software image on the router, check to see if the router meets the RAM memory and flash requirements for that image. To see the amount of RAM, issue the show version command:
…
Router user interface modes
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 and privileged EXEC mode:
• The user EXEC mode allows only a limited number of basic monitoring commands. This is often referred to as a view only mode. The user EXEC level does not allow any commands that might change the configuration of the router. The user EXEC mode can be identified by the > prompt.
• The privileged EXEC mode provides access to all router commands. This mode can be configured to require a password. For added protection, it can also be configured to require a user ID. This allows only authorized users to access the router. Configuration and management commands require that the network administrator be at the privileged EXEC level. Global configuration mode and all other more specific configuration modes can only be reached from the privileged EXEC mode. The privileged EXEC mode can be identified by the # prompt.
To access the privileged EXEC level from the user EXEC level, enter the enable command at the > prompt. If a password is configured, the router will then ask for that password. For security reasons, a Cisco network device will not show the password that is entered. When the correct password is entered, the router prompt will change to #. This indicates that the user is at the privileged EXEC level. When a question mark, ?, is entered at the privileged EXEC level, it will reveal many more command options than available at the user EXEC level.
The next page covers some additional features of Cisco IOS.
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 and privileged EXEC mode:
• The user EXEC mode allows only a limited number of basic monitoring commands. This is often referred to as a view only mode. The user EXEC level does not allow any commands that might change the configuration of the router. The user EXEC mode can be identified by the > prompt.
• The privileged EXEC mode provides access to all router commands. This mode can be configured to require a password. For added protection, it can also be configured to require a user ID. This allows only authorized users to access the router. Configuration and management commands require that the network administrator be at the privileged EXEC level. Global configuration mode and all other more specific configuration modes can only be reached from the privileged EXEC mode. The privileged EXEC mode can be identified by the # prompt.
To access the privileged EXEC level from the user EXEC level, enter the enable command at the > prompt. If a password is configured, the router will then ask for that password. For security reasons, a Cisco network device will not show the password that is entered. When the correct password is entered, the router prompt will change to #. This indicates that the user is at the privileged EXEC level. When a question mark, ?, is entered at the privileged EXEC level, it will reveal many more command options than available at the user EXEC level.
The next page covers some additional features of Cisco IOS.
Router user interface
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.
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 / The purpose of Cisco IOS software
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) session with the router
• Alternate between the user executive (EXEC) and privileged EXEC modes
• Establish a HyperTerminal session on a router
• Log into a router
• Use the help feature in the command line interface
• Troubleshoot command errors
The purpose of Cisco IOS software
2.1.1 As with a computer, a router or switch cannot function without an operating system. This page will review the Cisco IOS. It is the embedded software architecture in all of the Cisco routers and is also the operating system of the Catalyst switches. Without an operating system, the hardware does not have any capabilities. The Cisco IOS provides the following network services:
• Basic routing and switching functions
• Reliable and secure access to networked resources
• Network scalability
The next page will discuss the Cisco IOS environment for a router.
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) session with the router
• Alternate between the user executive (EXEC) and privileged EXEC modes
• Establish a HyperTerminal session on a router
• Log into a router
• Use the help feature in the command line interface
• Troubleshoot command errors
The purpose of Cisco IOS software
2.1.1 As with a computer, a router or switch cannot function without an operating system. This page will review the Cisco IOS. It is the embedded software architecture in all of the Cisco routers and is also the operating system of the Catalyst switches. Without an operating system, the hardware does not have any capabilities. The Cisco IOS provides the following network services:
• Basic routing and switching functions
• Reliable and secure access to networked resources
• Network scalability
The next page will discuss the Cisco IOS environment for a router.
Saturday, April 24, 2010
Summary of Module 1 Semester 2
Summary
This page summarizes the topics discussed in this module.
The major difference between a WAN and a LAN is the geographical area that is covered. A LAN connects workstations, printers, servers, and other devices within a building or other small area. A WAN is used to connect multiple LANs, typically over a large geographical area. The primary characteristics of a WAN include the ability to connect devices separated by wide geographical areas, the use of service companies to make these connections, and the serial connections used to access bandwidth.
There are several organizations that define and manage the standards used for WAN design such as ITU-T, ISO, IETF, and EIA.
WANs operate at the physical layer and the data link layer, which are Layers 1 and 2 of the OSI reference model. The devices used in a WAN, such as routers, CSU/DSUs, modems, and communication servers, operate at the physical layer. At the data link layer, the protocols determine how frames are carried between systems. A router can act as a LAN or a WAN device because it operates at the network layer, which is Layer 3.
Routers are specialized computers that use the Cisco IOS software to run configuration files. The main internal components of a router are as follows:
• The CPU, which executes instructions in the operating system
• RAM or DRAM to store the routing tables
• NVRAM to provide storage for the startup configuration file
• Flash memory to hold the IOS
• ROM for the POST
• Interfaces to connect to a PC or modem
There are three basic external connections on a router:
• LAN interface
• WAN interface
• Management interface
Management is used for the initial setup of the router and for troubleshooting. Most routers provide a console port, which is an EIA-232 asynchronous serial port. Some routers include an auxiliary port. A rollover cable and an RJ-45 to DB-9 adapter are used to connect the router console port to a PC.
In a LAN environment, the router is a host that communicates with the LAN through a hub or a switch. It is connected using a straight-through cable. A WAN is a little more complicated. The DTE is connected from the CPE to the service provider through a DCE device, which is typically a modem or CSU/DSU. This device converts the data from the DTE to a form recognized by the service provider. WAN services include leased line, circuit-switched, or packet-switched. Four considerations are used to select the proper cable:
• The type of connection to the Cisco device
• The type of network system that will be connected, which is DTE or DCE
• The signaling standard
• The type of connector on the cable
This page summarizes the topics discussed in this module.
The major difference between a WAN and a LAN is the geographical area that is covered. A LAN connects workstations, printers, servers, and other devices within a building or other small area. A WAN is used to connect multiple LANs, typically over a large geographical area. The primary characteristics of a WAN include the ability to connect devices separated by wide geographical areas, the use of service companies to make these connections, and the serial connections used to access bandwidth.
There are several organizations that define and manage the standards used for WAN design such as ITU-T, ISO, IETF, and EIA.
WANs operate at the physical layer and the data link layer, which are Layers 1 and 2 of the OSI reference model. The devices used in a WAN, such as routers, CSU/DSUs, modems, and communication servers, operate at the physical layer. At the data link layer, the protocols determine how frames are carried between systems. A router can act as a LAN or a WAN device because it operates at the network layer, which is Layer 3.
Routers are specialized computers that use the Cisco IOS software to run configuration files. The main internal components of a router are as follows:
• The CPU, which executes instructions in the operating system
• RAM or DRAM to store the routing tables
• NVRAM to provide storage for the startup configuration file
• Flash memory to hold the IOS
• ROM for the POST
• Interfaces to connect to a PC or modem
There are three basic external connections on a router:
• LAN interface
• WAN interface
• Management interface
Management is used for the initial setup of the router and for troubleshooting. Most routers provide a console port, which is an EIA-232 asynchronous serial port. Some routers include an auxiliary port. A rollover cable and an RJ-45 to DB-9 adapter are used to connect the router console port to a PC.
In a LAN environment, the router is a host that communicates with the LAN through a hub or a switch. It is connected using a straight-through cable. A WAN is a little more complicated. The DTE is connected from the CPE to the service provider through a DCE device, which is typically a modem or CSU/DSU. This device converts the data from the DTE to a form recognized by the service provider. WAN services include leased line, circuit-switched, or packet-switched. Four considerations are used to select the proper cable:
• The type of connection to the Cisco device
• The type of network system that will be connected, which is DTE or DCE
• The signaling standard
• The type of connector on the cable
Connecting WAN interfaces
Connecting WAN interfaces
1.2.7 This page discusses the different forms of WAN connections.
A WAN uses many different technologies to make data connections across a broad geographic area. WAN communication services are usually leased from service providers. WAN connection types include leased line, circuit-switched, and packet-switched.
For each type of WAN service, the customer premises equipment (CPE), which is often a router, is the DTE. This is connected to the service provider through a DCE device, which is commonly a modem or CSU/DSU. This device is used to convert the data from the DTE into a form acceptable to the WAN service provider.
Perhaps the most commonly used router interfaces for WAN services are serial interfaces. Answer the following questions to select the proper serial cable:
• What is the type of connection to the Cisco device? Cisco routers may use different connectors for the serial interfaces. The interface on the left is a Smart Serial interface. The interface on the right is a DB-60 connection. It is important to select the correct serial cable to connect the network system to the serial devices. This is a critical part in setting up a WAN.
• Is the network system connected to a DTE or DCE device? DTE and DCE are the two types of serial interfaces that devices use to communicate. The key difference between these two is that the DCE device provides the clock signal for the communications on the bus. The device documentation should specify whether it is DTE or DCE.
• Which signaling standard does the device require? For each different device, a different serial standard could be used. Each standard defines the signals on the cable and specifies the connector at the end of the cable. Device documentation should always be consulted for the signaling standard.
• Is a male or female connector required on the cable? If the connector has visible projecting pins, it is male. If the connector has sockets for projecting pins, it is female.
This page concludes Module 1. The next page will provide a summary of the main points from this module.
1.2.7 This page discusses the different forms of WAN connections.
A WAN uses many different technologies to make data connections across a broad geographic area. WAN communication services are usually leased from service providers. WAN connection types include leased line, circuit-switched, and packet-switched.
For each type of WAN service, the customer premises equipment (CPE), which is often a router, is the DTE. This is connected to the service provider through a DCE device, which is commonly a modem or CSU/DSU. This device is used to convert the data from the DTE into a form acceptable to the WAN service provider.
Perhaps the most commonly used router interfaces for WAN services are serial interfaces. Answer the following questions to select the proper serial cable:
• What is the type of connection to the Cisco device? Cisco routers may use different connectors for the serial interfaces. The interface on the left is a Smart Serial interface. The interface on the right is a DB-60 connection. It is important to select the correct serial cable to connect the network system to the serial devices. This is a critical part in setting up a WAN.
• Is the network system connected to a DTE or DCE device? DTE and DCE are the two types of serial interfaces that devices use to communicate. The key difference between these two is that the DCE device provides the clock signal for the communications on the bus. The device documentation should specify whether it is DTE or DCE.
• Which signaling standard does the device require? For each different device, a different serial standard could be used. Each standard defines the signals on the cable and specifies the connector at the end of the cable. Device documentation should always be consulted for the signaling standard.
• Is a male or female connector required on the cable? If the connector has visible projecting pins, it is male. If the connector has sockets for projecting pins, it is female.
This page concludes Module 1. The next page will provide a summary of the main points from this module.
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