Introduction to routers in a WAN
1.1.2 This page will provide a brief review of routers.
A router is a special type of computer. It has the same basic components as a standard desktop PC. It has a CPU, memory, a system bus, and various input/output interfaces. However, routers are designed to perform some very specific functions that are not typically performed by desktop computers. For example, routers connect and allow communication between two networks and determine the best path for data to travel through the connected networks.
Just as computers need operating systems to run software applications, routers need the Internetwork Operating System (IOS) software to run configuration files. These configuration files contain the instructions and parameters that control the flow of traffic in and out of the routers. Routers use routing protocols to determine the best path for packets. The configuration file specifies all the information for the correct setup and use of the selected, or enabled, routing and routed protocols on a router.
This course will demonstrate how to build configuration files from the IOS commands in order to get the router to perform many essential network functions. The router configuration file may seem complex at first, but it will be easier to understand by the end of the course.
The main internal components of the router are random-access memory (RAM), nonvolatile random-access memory (NVRAM), flash memory, read-only memory (ROM), and interfaces.
RAM has the following characteristics and functions:
• Stores routing tables
• Holds ARP cache
• Holds fast-switching cache
• Performs packet buffering as shared RAM
• Maintains packet-hold queues
• Provides temporary memory for the configuration file of a router while the router is powered on
• Loses content when a router is powered down or restarted
NVRAM has the following characteristics and functions:
• Provides storage for the startup configuration file
• Retains content when a router is powered down or restarted
Flash memory has the following characteristics and functions:
• Holds the IOS image
• Allows software to be updated without removing and replacing chips on the processor
• Retains content when a router is powered down or restarted
• Can store multiple versions of IOS software
• Is a type of electrically erasable programmable read-only memory (EEPROM)
ROM has the following characteristics and functions:
• Maintains instructions for power-on self test (POST) diagnostics
• Stores bootstrap program and basic operating system software
• Requires replacing pluggable chips on the motherboard for software upgrades
Interfaces have the following characteristics and functions:
• Connect routers to a network for packet entry and exit
• Can be on the motherboard or on a separate module
The next page will describe the role of routers in WANs and LANs.
Saturday, April 24, 2010
This page will provide a brief review of routers.
A router is a special type of computer. It has the same basic components as a standard desktop PC. It has a CPU, memory, a system bus, and various input/output interfaces. However, routers are designed to perform some very specific functions that are not typically performed by desktop computers. For example, routers connect and allow communication between two networks and determine the best path for data to travel through the connected networks.
Just as computers need operating systems to run software applications, routers need the Internetwork Operating System (IOS) software to run configuration files. These configuration files contain the instructions and parameters that control the flow of traffic in and out of the routers. Routers use routing protocols to determine the best path for packets. The configuration file specifies all the information for the correct setup and use of the selected, or enabled, routing and routed protocols on a router.
This course will demonstrate how to build configuration files from the IOS commands in order to get the router to perform many essential network functions. The router configuration file may seem complex at first, but it will be easier to understand by the end of the course.
The main internal components of the router are random-access memory (RAM), nonvolatile random-access memory (NVRAM), flash memory, read-only memory (ROM), and interfaces.
RAM has the following characteristics and functions:
Stores routing tables
Holds ARP cache
Holds fast-switching cache
Performs packet buffering as shared RAM
Maintains packet-hold queues
Provides temporary memory for the configuration file of a router while the router is powered on
Loses content when a router is powered down or restarted
NVRAM has the following characteristics and functions:
Provides storage for the startup configuration file
Retains content when a router is powered down or restarted
Flash memory has the following characteristics and functions:
Holds the IOS image
Allows software to be updated without removing and replacing chips on the processor
Retains content when a router is powered down or restarted
Can store multiple versions of IOS software
Is a type of electrically erasable programmable read-only memory (EEPROM)
ROM has the following characteristics and functions:
Maintains instructions for power-on self test (POST) diagnostics
Stores bootstrap program and basic operating system software
Requires replacing pluggable chips on the motherboard for software upgrades
Interfaces have the following characteristics and functions:
Connect routers to a network for packet entry and exit
Can be on the motherboard or on a separate module
The next page will describe the role of routers in WANs and LANs.
A router is a special type of computer. It has the same basic components as a standard desktop PC. It has a CPU, memory, a system bus, and various input/output interfaces. However, routers are designed to perform some very specific functions that are not typically performed by desktop computers. For example, routers connect and allow communication between two networks and determine the best path for data to travel through the connected networks.
Just as computers need operating systems to run software applications, routers need the Internetwork Operating System (IOS) software to run configuration files. These configuration files contain the instructions and parameters that control the flow of traffic in and out of the routers. Routers use routing protocols to determine the best path for packets. The configuration file specifies all the information for the correct setup and use of the selected, or enabled, routing and routed protocols on a router.
This course will demonstrate how to build configuration files from the IOS commands in order to get the router to perform many essential network functions. The router configuration file may seem complex at first, but it will be easier to understand by the end of the course.
The main internal components of the router are random-access memory (RAM), nonvolatile random-access memory (NVRAM), flash memory, read-only memory (ROM), and interfaces.
RAM has the following characteristics and functions:
Stores routing tables
Holds ARP cache
Holds fast-switching cache
Performs packet buffering as shared RAM
Maintains packet-hold queues
Provides temporary memory for the configuration file of a router while the router is powered on
Loses content when a router is powered down or restarted
NVRAM has the following characteristics and functions:
Provides storage for the startup configuration file
Retains content when a router is powered down or restarted
Flash memory has the following characteristics and functions:
Holds the IOS image
Allows software to be updated without removing and replacing chips on the processor
Retains content when a router is powered down or restarted
Can store multiple versions of IOS software
Is a type of electrically erasable programmable read-only memory (EEPROM)
ROM has the following characteristics and functions:
Maintains instructions for power-on self test (POST) diagnostics
Stores bootstrap program and basic operating system software
Requires replacing pluggable chips on the motherboard for software upgrades
Interfaces have the following characteristics and functions:
Connect routers to a network for packet entry and exit
Can be on the motherboard or on a separate module
The next page will describe the role of routers in WANs and LANs.
Friday, March 26, 2010
WANs / Introduction to WANs
Introduction to WANs
1.1.1 A WAN is a data communications network that spans a large geographic area such as a state, province, or country. WANs often use transmission facilities provided by common carriers such as telephone companies.
These are the major characteristics of WANs:
They connect devices that are separated by wide geographical areas.
They use the services of carriers such as the Regional Bell Operating Companies (RBOCs), Sprint, MCI, and VPM Internet Services, Inc. to establish the link or connection between sites.
They use serial connections of various types to access bandwidth over large geographic areas.
A WAN differs from a LAN in several ways. For example, unlike a LAN, which connects workstations, peripherals, terminals, and other devices in a single building, a WAN makes data connections across a broad geographic area. Companies use a WAN to connect various company sites so that information can be exchanged between distant offices.
A WAN operates at the physical layer and the data link layer of the OSI reference model. It interconnects LANs that are usually separated by large geographic areas. WANs provide for the exchange of data packets and frames between routers and switches and the LANs they support.
The following devices are used in WANs:
Routers offer many services, including internetworking and WAN interface ports.
Modems include interface voice-grade services, channel service units/digital service units (CSU/DSUs) that interface T1/E1 services, and Terminal Adapters/Network Termination 1 (TA/NT1s) that interface Integrated Services Digital Network (ISDN) services.
Communication servers concentrate dial in and dial out user communication.
WAN data link protocols describe how frames are carried between systems on a single data link. They include protocols designed to operate over dedicated point-to-point, multipoint, and multi-access switched services such as Frame Relay. WAN standards are defined and managed by a number of recognized authorities, including the following agencies:
International Telecommunication Union-Telecommunication Standardization Sector (ITU-T), formerly the Consultative Committee for International Telegraph and Telephone (CCITT)
International Organization for Standardization (ISO)
Internet Engineering Task Force (IETF)
Electronic Industries Association (EIA)
The next page will describe routers. This information is important to further understand WANs.
1.1.1 A WAN is a data communications network that spans a large geographic area such as a state, province, or country. WANs often use transmission facilities provided by common carriers such as telephone companies.
These are the major characteristics of WANs:
They connect devices that are separated by wide geographical areas.
They use the services of carriers such as the Regional Bell Operating Companies (RBOCs), Sprint, MCI, and VPM Internet Services, Inc. to establish the link or connection between sites.
They use serial connections of various types to access bandwidth over large geographic areas.
A WAN differs from a LAN in several ways. For example, unlike a LAN, which connects workstations, peripherals, terminals, and other devices in a single building, a WAN makes data connections across a broad geographic area. Companies use a WAN to connect various company sites so that information can be exchanged between distant offices.
A WAN operates at the physical layer and the data link layer of the OSI reference model. It interconnects LANs that are usually separated by large geographic areas. WANs provide for the exchange of data packets and frames between routers and switches and the LANs they support.
The following devices are used in WANs:
Routers offer many services, including internetworking and WAN interface ports.
Modems include interface voice-grade services, channel service units/digital service units (CSU/DSUs) that interface T1/E1 services, and Terminal Adapters/Network Termination 1 (TA/NT1s) that interface Integrated Services Digital Network (ISDN) services.
Communication servers concentrate dial in and dial out user communication.
WAN data link protocols describe how frames are carried between systems on a single data link. They include protocols designed to operate over dedicated point-to-point, multipoint, and multi-access switched services such as Frame Relay. WAN standards are defined and managed by a number of recognized authorities, including the following agencies:
International Telecommunication Union-Telecommunication Standardization Sector (ITU-T), formerly the Consultative Committee for International Telegraph and Telephone (CCITT)
International Organization for Standardization (ISO)
Internet Engineering Task Force (IETF)
Electronic Industries Association (EIA)
The next page will describe routers. This information is important to further understand WANs.
CCNA 2 :- Module 1 Router and Routing Basic Overview
Overview
A wide-area network (WAN) is a data communications network that connects user networks over a large geographical area. WANs have several important characteristics that distinguish them from LANs. The first lesson in this module will provide an overview of WAN technologies and protocols. It will also explain how WANs and LANs are different, and ways in which they are similar.
It is important to understand the physical layer components of a router. This knowledge builds a foundation for other information and skills that are needed to configure routers and manage routed networks. This module provides a close examination of the internal and external physical components of the router. The module also describes techniques for physically connecting the various router interfaces.
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:
A wide-area network (WAN) is a data communications network that connects user networks over a large geographical area. WANs have several important characteristics that distinguish them from LANs. The first lesson in this module will provide an overview of WAN technologies and protocols. It will also explain how WANs and LANs are different, and ways in which they are similar.
Students who complete this module should be able to perform the following tasks:
- Identify organizations responsible for WAN standards
- Explain the difference between a WAN and LAN and the type of standards and protocols each uses
- Describe the role of a router in a WAN
- Identify internal components of the router and describe their functions
- Describe the physical characteristics of the router
- Identify LAN and management ports on a router
- Properly connect Ethernet, serial WAN, and console ports
Thursday, March 25, 2010
Notice for all viewers :)
Notice
The first semester of CCNA has publised with 11 Chapter. Please send feed back on my email, if all reader of have any question, please must write back. I feel happy.
The second semester will update after few days, this is under process. Hope all will enjoy.
Aqeel Haider
(Writer)
The first semester of CCNA has publised with 11 Chapter. Please send feed back on my email, if all reader of have any question, please must write back. I feel happy.
The second semester will update after few days, this is under process. Hope all will enjoy.
Aqeel Haider
(Writer)
Summary of Module 11
Summary
This page summarizes the topics discussed in this module.
The primary duties of the transport layer, Layer 4 of the OSI model, are to transport and regulate the flow of information from the source to the destination reliably and accurately.
The transport layer multiplexes data from upper layer applications into a stream of data packets. It uses port (socket) numbers to identify different conversations and delivers the data to the correct application.
The Transmission Control Protocol (TCP) is a connection-oriented transport protocol that provides flow control as well as reliability. TCP uses a three-way handshake to establish a synchronized circuit between end-user applications. Each datagram is numbered before transmission. At the receiving station, TCP reassembles the segments into a complete message. If a sequence number is missing in the series, that segment is retransmitted.
Flow control ensures that a transmitting node does not overwhelm a receiving node with data. The simplest method of flow control used by TCP involves a “not ready” signal that notifies the transmitting device that the buffers on the receiving device are full. When the receiver can handle additional data, the receiver sends a “ready” transport indicator.
Positive acknowledgment with retransmission is another TCP protocol technique that guarantees reliable delivery of data. Because having to wait for an acknowledgment after sending each packet would negatively impact throughput, windowing is used to allow multiple packets to be transmitted before an acknowledgment is received. TCP window sizes are variable during the lifetime of a connection.
Positive acknowledgment with retransmission is another TCP protocol technique that guarantees reliable delivery of data. Because having to wait for an acknowledgment after sending each packet would negatively impact throughput, windowing is used to allow multiple packets to be transmitted before an acknowledgment is received. TCP window sizes are variable during the lifetime of a connection.
If an application does not require flow control or an acknowledgment, as in the case of a broadcast transmission, User Datagram Protocol (UDP) can be used instead of TCP. UDP is a connectionless transport protocol in the TCP/IP protocol stack that allows multiple conversations to occur simultaneously but does not provide acknowledgments or guaranteed delivery. A UDP header is much smaller than a TCP header because of the lack of control information it must contain.
Some of the protocols and applications that function at the application level are well known to Internet users:
• Domain Name System (DNS) - Used in IP networks to translate names of network nodes into IP addresses
• File Transfer Protocol (FTP) - Used for transferring files between networks
• Hypertext Transfer Protocol (HTTP) - Used to deliver hypertext markup language (HTML) documents to a client application, such as a WWW browser
• Simple Mail Transfer Protocol (SMTP) - Used to provide electronic mail services
• Simple Network Management Protocol (SNMP) - Used to monitor and control network devices and to manage configurations, statistics collection, performance and security
• Telnet - Used to login to a remote host that is running a Telnet server application and then to execute commands from the command line
This page summarizes the topics discussed in this module.
The primary duties of the transport layer, Layer 4 of the OSI model, are to transport and regulate the flow of information from the source to the destination reliably and accurately.
The transport layer multiplexes data from upper layer applications into a stream of data packets. It uses port (socket) numbers to identify different conversations and delivers the data to the correct application.
The Transmission Control Protocol (TCP) is a connection-oriented transport protocol that provides flow control as well as reliability. TCP uses a three-way handshake to establish a synchronized circuit between end-user applications. Each datagram is numbered before transmission. At the receiving station, TCP reassembles the segments into a complete message. If a sequence number is missing in the series, that segment is retransmitted.
Flow control ensures that a transmitting node does not overwhelm a receiving node with data. The simplest method of flow control used by TCP involves a “not ready” signal that notifies the transmitting device that the buffers on the receiving device are full. When the receiver can handle additional data, the receiver sends a “ready” transport indicator.
Positive acknowledgment with retransmission is another TCP protocol technique that guarantees reliable delivery of data. Because having to wait for an acknowledgment after sending each packet would negatively impact throughput, windowing is used to allow multiple packets to be transmitted before an acknowledgment is received. TCP window sizes are variable during the lifetime of a connection.
Positive acknowledgment with retransmission is another TCP protocol technique that guarantees reliable delivery of data. Because having to wait for an acknowledgment after sending each packet would negatively impact throughput, windowing is used to allow multiple packets to be transmitted before an acknowledgment is received. TCP window sizes are variable during the lifetime of a connection.
If an application does not require flow control or an acknowledgment, as in the case of a broadcast transmission, User Datagram Protocol (UDP) can be used instead of TCP. UDP is a connectionless transport protocol in the TCP/IP protocol stack that allows multiple conversations to occur simultaneously but does not provide acknowledgments or guaranteed delivery. A UDP header is much smaller than a TCP header because of the lack of control information it must contain.
Some of the protocols and applications that function at the application level are well known to Internet users:
• Domain Name System (DNS) - Used in IP networks to translate names of network nodes into IP addresses
• File Transfer Protocol (FTP) - Used for transferring files between networks
• Hypertext Transfer Protocol (HTTP) - Used to deliver hypertext markup language (HTML) documents to a client application, such as a WWW browser
• Simple Mail Transfer Protocol (SMTP) - Used to provide electronic mail services
• Simple Network Management Protocol (SNMP) - Used to monitor and control network devices and to manage configurations, statistics collection, performance and security
• Telnet - Used to login to a remote host that is running a Telnet server application and then to execute commands from the command line
SMTP / SNMP / Telnet
SMTP
11.2.5 This page will discuss the features of SMTP.
Email servers communicate with each other using the Simple Mail Transfer Protocol (SMTP) to send and receive mail. The SMTP protocol transports email messages in ASCII format using TCP.
When a mail server receives a message destined for a local client, it stores that message and waits for the client to collect the mail. There are several ways for mail clients to collect their mail. They can use programs that access the mail server files directly or collect their mail using one of many network protocols. The most popular mail client protocols are POP3 and IMAP4, which both use TCP to transport data. Even though mail clients use these special protocols to collect mail, they almost always use SMTP to send mail. Since two different protocols, and possibly two different servers, are used to send and receive mail, it is possible that mail clients can perform one task and not the other. Therefore, it is usually a good idea to troubleshoot e-mail sending problems separately from e-mail receiving problems.
When checking the configuration of a mail client, verify that the SMTP and POP or IMAP settings are correctly configured. A good way to test if a mail server is reachable is to Telnet to the SMTP port (25) or to the POP3 port (110). The following command format is used at the Windows command line to test the ability to reach the SMTP service on the mail server at IP address 192.168.10.5:
C:\>telnet 192.168.10.5 25
The SMTP protocol does not offer much in the way of security and does not require any authentication. Administrators often do not allow hosts that are not part of their network to use their SMTP server to send or relay mail. This is to prevent unauthorized users from using their servers as mail relays.
The next page will describe the features of SNMP.
SNMP
11.2.6 This page will define SNMP.
The Simple Network Management Protocol (SNMP) is an application layer protocol that facilitates the exchange of management information between network devices. SNMP enables network administrators to manage network performance, find and solve network problems, and plan for network growth. SNMP uses UDP as its transport layer protocol.
An SNMP managed network consists of the following three key components:
• Network management system (NMS) – NMS executes applications that monitor and control managed devices. The bulk of the processing and memory resources required for network management are provided by NMS. One or more NMSs must exist on any managed network.
• Managed devices – Managed devices are network nodes that contain an SNMP agent and that reside on a managed network. Managed devices collect and store management information and make this information available to NMSs using SNMP. Managed devices, sometimes called network elements, can be routers, access servers, switches, and bridges, hubs, computer hosts, or printers.
• Agents – Agents are network-management software modules that reside in managed devices. An agent has local knowledge of management information and translates that information into a form compatible with SNMP.
The next page will describe Telnet.
Telnet
11.2.7 This page will explain the features of Telnet.
Telnet client software provides the ability to login to a remote Internet host that is running a Telnet server application and then to execute commands from the command line. A Telnet client is referred to as a local host. Telnet server, which uses special software called a daemon, is referred to as a remote host.
To make a connection from a Telnet client, the connection option must be selected. A dialog box typically prompts for a host name and terminal type. The host name is the IP address or DNS name of the remote computer. The terminal type describes the type of terminal emulation that the Telnet client should perform. The Telnet operation uses none of the processing power from the transmitting computer. Instead, it transmits the keystrokes to the remote host and sends the resulting screen output back to the local monitor. All processing and storage take place on the remote computer.
Telnet works at the application layer of the TCP/IP model. Therefore, Telnet works at the top three layers of the OSI model. The application layer deals with commands. The presentation layer handles formatting, usually ASCII. The session layer transmits. In the TCP/IP model, all of these functions are considered to be part of the application layer.
This page concludes this lesson. The next page will summarize the main points from the module.
11.2.5 This page will discuss the features of SMTP.
Email servers communicate with each other using the Simple Mail Transfer Protocol (SMTP) to send and receive mail. The SMTP protocol transports email messages in ASCII format using TCP.
When a mail server receives a message destined for a local client, it stores that message and waits for the client to collect the mail. There are several ways for mail clients to collect their mail. They can use programs that access the mail server files directly or collect their mail using one of many network protocols. The most popular mail client protocols are POP3 and IMAP4, which both use TCP to transport data. Even though mail clients use these special protocols to collect mail, they almost always use SMTP to send mail. Since two different protocols, and possibly two different servers, are used to send and receive mail, it is possible that mail clients can perform one task and not the other. Therefore, it is usually a good idea to troubleshoot e-mail sending problems separately from e-mail receiving problems.
When checking the configuration of a mail client, verify that the SMTP and POP or IMAP settings are correctly configured. A good way to test if a mail server is reachable is to Telnet to the SMTP port (25) or to the POP3 port (110). The following command format is used at the Windows command line to test the ability to reach the SMTP service on the mail server at IP address 192.168.10.5:
C:\>telnet 192.168.10.5 25
The SMTP protocol does not offer much in the way of security and does not require any authentication. Administrators often do not allow hosts that are not part of their network to use their SMTP server to send or relay mail. This is to prevent unauthorized users from using their servers as mail relays.
The next page will describe the features of SNMP.
SNMP
11.2.6 This page will define SNMP.
The Simple Network Management Protocol (SNMP) is an application layer protocol that facilitates the exchange of management information between network devices. SNMP enables network administrators to manage network performance, find and solve network problems, and plan for network growth. SNMP uses UDP as its transport layer protocol.
An SNMP managed network consists of the following three key components:
• Network management system (NMS) – NMS executes applications that monitor and control managed devices. The bulk of the processing and memory resources required for network management are provided by NMS. One or more NMSs must exist on any managed network.
• Managed devices – Managed devices are network nodes that contain an SNMP agent and that reside on a managed network. Managed devices collect and store management information and make this information available to NMSs using SNMP. Managed devices, sometimes called network elements, can be routers, access servers, switches, and bridges, hubs, computer hosts, or printers.
• Agents – Agents are network-management software modules that reside in managed devices. An agent has local knowledge of management information and translates that information into a form compatible with SNMP.
The next page will describe Telnet.
Telnet
11.2.7 This page will explain the features of Telnet.
Telnet client software provides the ability to login to a remote Internet host that is running a Telnet server application and then to execute commands from the command line. A Telnet client is referred to as a local host. Telnet server, which uses special software called a daemon, is referred to as a remote host.
To make a connection from a Telnet client, the connection option must be selected. A dialog box typically prompts for a host name and terminal type. The host name is the IP address or DNS name of the remote computer. The terminal type describes the type of terminal emulation that the Telnet client should perform. The Telnet operation uses none of the processing power from the transmitting computer. Instead, it transmits the keystrokes to the remote host and sends the resulting screen output back to the local monitor. All processing and storage take place on the remote computer.
Telnet works at the application layer of the TCP/IP model. Therefore, Telnet works at the top three layers of the OSI model. The application layer deals with commands. The presentation layer handles formatting, usually ASCII. The session layer transmits. In the TCP/IP model, all of these functions are considered to be part of the application layer.
This page concludes this lesson. The next page will summarize the main points from the module.
Subscribe to:
Posts (Atom)
