Computer Networks CCNA 1 & 2. 3 rd Stage. Academic Year Lecturer AWDANG AZIZ HUSSIN

Transcription

1 Lavin institute CCNA1&2 Computer Networks CCNA 1 & 2 3 rd Stage Academic Year Lecturer AWDANG AZIZ HUSSIN Connect us: instlaven.weebly.com 1

2 Networking Fundamentals a network is a group of connected devices, such as computers and printer, that communicate either wirelessly or via a cable. Computer networks are no longer relegated to allowing a group of computers to access a common set of files stored on a computer designated as a file server. Instead, with the building of high-speed, highly redundant networks, network architects are seeing the wisdom of placing a variety of traffic types on a single network. Examples include voice and video, in addition to data. The Purpose of Networks At its essence, a network s purpose is to make connections. These connections might be between a PC and a printer or between a laptop and the Internet, as just a couple of examples. However, the true value of a network comes from the traffic flowing over those connections. Consider a sampling of applications that can travel over a network s connections: File sharing between two computers. Video chatting between computers located in different parts of the world. Surfing the web (for example, to use social media sites, watch streaming video, or to listen to an Internet radio station). Instant messaging (IM) between computers with IM software installed. 2

3 . Voice over IP (VoIP), to replace traditional telephony systems. A term commonly given to a network transporting multiple types of traffic (for example, voice, video, and data) is a converged network. A converged network might offer significant cost savings to organizations that previously supported separate network infrastructures for voice, data, and video traffic. This convergence can also potentially reduce staffing costs, because only a single network needs to be maintained, rather than separate networks for separate traffic types. Primary Building Blocks used to Construct Network The webs of data or information networks vary in size and capabilities, but all networks have four basic elements in common: Rules or agreements: Rules or agreements (protocols) govern how the messages are sent, directed, received, and interpreted. Messages: The messages or units of information travel from one device to another. Medium: A medium is a means of interconnecting these devices, that is, a medium can transport the messages from one device to another. Devices: Devices on the network exchange messages with each other. 3

4 Early networks had varying standards and, as a result, could not communicate easily with each other. Now global standardization of these elements enables easy communication between networks regardless of the equipment manufacturer. Common Terms used in Computer Network Designing, installing, administering, and troubleshooting a network requires the ability to recognize various network terms. 4

5 The following list describes the network components and the functions they serve: Client: The term client defines the device an end user uses to access a network. This device might be a workstation, laptop, smartphone with wireless capabilities, or a variety of other end-user terminal devices. Server: A server, as the name suggests, serves up resources to a network. These resources might include access as provided by an server, web pages as provided by a web server, or files available on a file server. Interconnecting Device: Devices such as switch or hub that interconnect network components, such as clients and servers. A hub is an older and slower interconnect device. Like a hub, a switch connects computers in a network but switch tracks the location of the computers on network and is faster than hub. Router is also Interconnecting device that interconnects two or more networks. Network Interface Card (NIC): A device that allows computers to connect to network. Media: The network devices need to be interconnected via some sort of media. The medium that physically carries the message can change several times between the sender and the receiver. Network connections can be wired or wireless. In wired connections, the medium is either copper, which carries electrical signals, or optical fiber, which carries light signals. In wireless connections, 5

6 the medium is the Earth s atmosphere, or space, and the signals are radio waves. Standard: A network standard is in short a reference model to make sure products of different vendors can work together in a network, The International Organization for Standardization (ISO) lays out and those standards. Protocol: In networking, the specification of a set of rules for a particular type of communication. The term is also used to refer to the software that implements a protocol. Computer Networking Models One way to categorize networks is based on where network resources reside. There are two networking models: 1-Peer-to-Peer Networks. Peer-to-peer networks allow interconnected devices (for example, PCs) to share their resources with one another. Those resources could be, for example, files or printers Peer-to-peer networks are commonly seen in smaller businesses and in homes. The popularity of these peer-to-peer networks is fueled in part by client operating systems that support file and print sharing. Scalability for peer-to-peer networks is a concern, however. Specifically, as the number of devices (that is, peers) increases, the administration burden increases. For example, a network administrator might have to manage file permissions on multiple devices, as opposed to a single server. 6

7 . Advantages of Peer-to-Peer Networks Cost Because peer-to-peer networking does not require a dedicated server. Ease of installation The built-in support for peer-to-peer networking in modern operating systems makes installing and configuring a peer-to-peer network a straightforward process. Maintenance A small peer-to-peer network is easy to maintain and does not require specialized staff or training. Disadvantages of Peer-to-Peer Networks Security In a decentralized model, a network wide security policy cannot be enforced from a server; rather, security needs to be applied to each computer and resource individually. 7

8 Data backup Because files and data are located on individual computers, each system must have its data backed up individually. Limited numbers of computers Peer-to-peer networking is effective only on small networks (fewer than 10 computers). 2- Client-Server Networks. Client/server networks are commonly used by businesses. Because resources are located on one or more servers, administration is simpler than trying to administer network resources on multiple peer devices. Advantages of Client-Server Networks Centralized management and security The ability to manage the network from a single location. Scalability In a server-based network, administrators can easily add computers and devices. 8

9 Simplified backups On server-based networks, files and folders typically reside in a single location. Disadvantages of Client-Server Networks High cost A server-based network requires additional hardware and software. Administration requirements Client/server networks require additional administrative skills. Single point of failure- If the server fails, the clients can t access the services that reside on the server. Network Topology A network topology graphically displays the interconnection methods used between devices. Topology can be logical or physical. Logical topology refers to the way that data travels from one device to another and largely determined by access method. Physical topology refers to the physical layout of devices and how are they cabled. There are several network topologies such are: Bus. Star. Ring. Mesh. 9

10 Bus Topology A bus topology, as depicted in Figure, typically uses a cable running through the area requiring connectivity. Devices that need to connect to the network then tap into this nearby cable. Early Ethernet networks commonly relied on bus topologies. Bus Topology- Advantages and Disadvantages Advantages: It is inexpensive and easy to implement. It doesn t require special equipment. It requires less cable than other topologies. Disadvantages: It cannot be expanded easily. Doing so may render the network inaccessible while the expansion is performed. A break in the cable renders the entire segment unusable. It is difficult to troubleshoot. 10

11 Star Topology In star topology every device uses an individual cable to connect to a central point (Hub or Switch). The star topology is the most popular physical topology in use today, with a switch at the center of the star and unshielded twisted-pair cable (UTP) used to connect from the switch ports to clients. Star Topology- Advantages and Disadvantages Advantages: It can be easily expanded without disruption to existing systems. A cable failure affects only a single system. It is easy to troubleshoot. Disadvantages: It requires additional networking equipment and more cables than bus. Centralized devices create a single point of failure 11

12 Ring Topology In ring topology traffic flows in a circular fashion around a closed network loop (that is, a ring). Typically, a ring topology sends data, in a single direction, to each connected device in turn, until the intended destination receives the data. Ring Topology- Advantages and Disadvantages Advantages: A dual ring topology adds a layer of fault tolerance. Disadvantages: A cable network break can disrupt the entire network. Also adding or removing computers to the network creates network disruption for all users. 12

13 Mesh Topology In Mesh topology each device connects directly to every other device. A full mesh uses point-to-point connectivity between all devices however a partial mesh uses point-to-point connectivity between devices, but not all of them.. Mesh Topology- Advantages and Disadvantages Advantages: Multiple links provide fault tolerance and redundancy. The network can be expanded with minimal or no disruption. Disadvantages: It is difficult to implement. It can be expensive. 13

14 Network Categories Based on the geographic dispersion of network components, networks can be classified into various categories, including the following: Local-Area Network (LAN) Wide-Area Network (WAN) Campus-Area Network (CAN) Metropolitan-Area Network (MAN) Personal-Area Network (PAN) Local Area Network (LAN) A LAN interconnects network components within a local region (for example, within a building). Examples of common LAN technologies are Ethernet and wireless LAN networks. 14

15 Wide Area Network (WAN) A WAN interconnects network components that are geographically separated. For example, a corporate headquarters might have multiple WAN connections to remote office sites. Asynchronous Transfer Mode (ATM), and Frame Relay are examples of WAN technologies. Metropolitan Area Network (MAN) A MAN is confined to a certain geographic area, such as a city. A MAN is almost always bigger than a LAN and usually smaller than or equal to a WAN. Metro Ethernet is an example of a MAN technology. Campus Area Network (CAN) A CAN is a network that spans a defined single location (such as an office complex with multiple buildings or a college campus) but is not large enough to be considered a MAN. Metro Ethernet is an example of a MAN technology. 15

16 Personal Area Network (PAN) A PAN is a network whose scale is even smaller than a LAN. As an example, a connection between a PC and a digital camera via a universal serial bus (USB) cable could be considered a PAN. A PAN, could be a wireless connection. Bluetooth connection between your cell phone and your car s audio system is considered a wireless PAN (WPAN). The main distinction of a PAN, however, is that its range is typically limited to just a few meters. Network Infrastructure Devices Computers and printers within a network are connected to various network devices such as: - Hub. Switch. Router. Access point. Bridge. Hubs Hub is a simple connection network device & has no intelligence. a hub does not make forwarding decisions. Instead, a hub receives bits in on one port and then retransmits those bits out all other ports. Hub can operate in half-duplex mode. data can be either sent or received on the wire but not at the same time. 16

17 The two basic types of Ethernet hubs are as follows: Passive hub: Does not amplify (that is, electrically regenerate) received bits. Active hub: Regenerates incoming bits as they are sent out all the ports on a hub, other than the port on which the bits were received. Switches Switches are intelligence devices and faster than hub. They can identify which device is connected to each physical port, based on the Media Access Control (MAC) address. Switch can operate in both half-duplex and full-duplex mode. Switch provides better performance & adds some security. 17

18 Routers Router is an intelligence device used to connect networks. they use the IP address to determine the best path. 18

19 Bridge A bridge joins two or more LAN segments, typically two Ethernet LAN segments. An Ethernet bridge can be used to scale Ethernet networks to a larger number of attached devices. Access Points A wireless access point (WAP) is sometimes referred to as simply an access point. Access points provide access to wired networks for wireless clients. 19

20 Open System Interconnection (OSI) Reference Model OSI model is a framework for network communication. It defines how data is handled at several different layers. The ISO created and it includes seven layers with specific activities, protocols, and devices working on each. One of the primary goals of the OSI Model is operating system independence. The OSI reference model has the following seven layers: Application layer (layer 7) Presentation layer (layer 6) Session layer (layer 5) Transport layer (layer 4) Network layer (layer 3) Data Link layer (layer 2) Physical layer (layer 1) 20

21 At the physical layer, a series of 1s and 0s represent data. At upper layers, however, bits are grouped together, into what is known as a protocol data unit (PDU) or a data service unit. Application Layer Application layer provides an interface for users to interact with application service or networking service such Web browser, Telnet etc. Several protocols operate on the Application layer. such AS HTTP, FTP, DNS and DHCP. Presentation Layer Determines how to format and present the data. Major functions of Presentation Layer: -Encoding & Decoding using ASCII, EBCDIC. 21

22 -Encryption & Decryption. -Compression & Decompression. Session Layer Responsible for establishing, maintaining, and terminating sessions. A session is simply a lasting connection between two networking devices. Two network protocols that operate on this layer are the Network Basic Input/output System (NetBIOS) and Remote Procedure Call (RPC). Transport Layer It is responsible for transporting data. this layer divides data into smaller chunks called segments and then reassembles the received data. Major Functions: -. Segmentation. Sequencing & Reassembling. Error Correction & Flow Control. 22

23 Transport Layer Protocols TCP Transmission Control Protocol Connection oriented Supports ACK Reliable communication Slower data transmission Eg: HTTP, FTP, SMTP UDP User Datagram Protocol Connection less No Supports for ACK Unreliable communication Faster data transmission Eg: DNS, DHCP, TFTP 23

24 Network Layer The Network layer is responsible for determining the best route to a destination. It uses routing protocols to build routing tables and uses Internet Protocol (IP) as the routed protocol. IP addresses are used at this layer to ensure the data can get to its destination. Data traveling on the Network layer is referred to as packets. The device that works at network layer is called Router. Data Link Layer The Data Link layer is concerned with data delivery on a local area network (LAN). Data traveling on the Data Link layer is referred to as frames. Media Access Control (MAC) defines how packets are placed onto the physical media at the Physical layer. The MAC address is also called a physical address, hardware address, burned-in address, or Ethernet address. Physical devices operating on the Data Link layer include bridges, switches, and NICs. Physical Layer The Physical layer defines the physical specifications of the network, such as cables and connectors. Data traveling on the Physical layer is converted to bits, or ones and zeros (such as ). Devices that work at physical layer are hubs and repeaters. 24

25 Transmission Control Protocol/ Internet Protocol (TCP/ IP) Reference Model The TCP/IP Model is a four-layer model created in the 1970s by the U.S. Department of Defense (DoD). The TCP/IP Model works similarly to the OSI Model. The TCP/IP model is basically a condensed version of the OSI model that comprises four instead of seven layers: Process/Application layer Host-to-Host layer/or Transport Internet layer Network Access layer/or Link 25

26 TCP/IP Model Layers and Protocols Application Layer: Protocols on this layer are used by applications to access network resources. Protocols include DNS, HTTP, FTP, SMTP, POP3, IMAP4, and SNMP. Transport Layer: Protocols on this layer control data transfer on the network by managing sessions between devices. The two primary protocols are TCP and UDP. It is also known as the host-to-host layer. Internet Layer: Protocols on the Internet layer control the movement and routing of packets between networks. Protocols on this layer include IPv4, IPv6, IGMP, ICMP, and ARP. Link Layer: This layer defines how data is transmitted onto the media. It includes multiple protocols such as Ethernet, token ring, frame relay, and ATM.The Link layer is also known as the Network Interface or Network Access layer. 26

27 Data Encapsulation When a host transmits data across a network to another device, the data goes through a process called encapsulation and is wrapped with protocol information at each layer of the OSI model. Each layer communicates only with its peer layer on the receiving device. To communicate and exchange information, each layer uses protocol data units (PDUs). These hold the control information attached to the data at each layer of the model. They are usually attached to the header in front of the data field but can also be at the trailer, or end, of it. Each PDU attaches to the data by encapsulating it at each layer of the OSI model, and each has a specific name depending on the information provided in each header. This PDU information is read-only by the peer layer on the receiving device. After its read, it s stripped off and the data is then handed to the next layer up. 27

28 Binary, Hexadecimal and Decimal Numbering System Binary System: The digits used are limited to either a 1 or a 0, and each digit is called a bit, which is short for binary digit. Typically, you group either 4 or 8 bits together, with these being referred to as a nibble and a byte, respectively. Decimal System: is a numbering system that we use in daily life. In a Base- 10 numbering system, there are ten digits, in the range of 0 through 9. Converting a Binary Number to a Decimal Number To convert a binary number to a decimal number, you populate the binary table with the given binary digits. Then you add up the column heading values for those columns containing a 1. For example, consider table below. Only the 128, 16, 4, and 2 columns contain a 1, and all the other columns contain a 0. If you add all the column headings containing a 1 in their column (that is, ), you get a result of 150. Therefore, you can conclude that the binary number of equates to a decimal value of

29 Converting a Decimal Number to a Binary Number To convert numbers from decimal to binary, staring with the leftmost column, ask the question, Is this number equal to or greater than the column heading? If the answer to that question is no, place a 0 in that column and move to the next column. If the answer is yes, place a 1 in that column and subtract the value of the column heading from the number you are converting. When you then move to the next column (to your right), again ask yourself, Is this number (which is the result of your previous subtraction) equal to or greater than the column heading? This process continues (to the right) for all the remaining column headings. For example, imagine that you want to convert the number 167 to binary. You can now conclude that a decimal number of 167 equates to a binary value of In fact, you can check your work by adding up the values for the column headings that contain a 1 in their column. In this example, the 128, 32, 4, 2, and 1 columns contain a 1. If you add these values, the result is 167 (that is, = 167). 29

30 Binary to decimal memorization chart Hexadecimal System: is a numbering system that uses the characters 0 through 9. Because the numbers 10, 11, 12, and so on can t be used (because they are two-digit numbers), the letters A, B, C, D, E, and F are used instead to represent 10, 11, 12, 13, 14, and 15, respectively. Hexadecimal Value Binary Value Decimal Value

31 A B C D E F IPv4 Addressing An IP address is a numeric identifier assigned to each machine on an IP network. It designates the specific location of a device on the network. An IP address is a software address, not a hardware address the latter is hard-coded on a network interface card (NIC) and used for finding hosts on a local network. IP addressing was designed to allow hosts on one network to communicate with a host on a different network regardless of the type of LANs the hosts are participating in. 31

32 IPv4 Address Structure An IPv4 address is a 32-bit address. However, rather than writing out each individual bit value, the address is typically written in dotted-decimal notation. Consider the IP address of This address is written in dotted-decimal notation. Notice that the IP address is divided into four separate numbers, separated by periods. Each number represents one-fourth of the IP address. Specifically, each number represents an 8-bit portion of the 32 bits in the address. Because each of these four divisions of an IP address represent 8 bits, these divisions are called octets. Interestingly, an IP address is composed of two types of addresses: a network address and a host address. Specifically, a group of contiguous left-justified bits represent the network address, and the remaining bits (that is, a group of contiguous right-justified bits) represent the address of a host on a network. The IP address component that determines which bits refer to the network and which bits refer to the host is called the subnet mask. You can think of the subnet mask as a dividing line separating an IP addresses 32 bits into a group of network bits (on the left) and a group of host bits (on the right). 32

33 A subnet mask typically consists of a series of contiguous 1s followed by a set of continuous 0s. In total, a subnet mask contains 32 bits, which correspond to the 32 bits found in an IPv4 address. The 1s in a subnet mask correspond to network bits in an IPv4 address, and 0s in a subnet mask correspond to host bits in an IPv4 address. The designers of the Internet decided to create classes of networks based on network size. For the small number of networks possessing a very large number of nodes, they created the rank Class A network. At the other extreme is the Class C network, which is reserved for the numerous networks with a small number of nodes. The class distinction for medium size networks is called the Class B. 33

34 Public & Private IP Address The people who created the IP addressing scheme also created private IP addresses. These addresses can be used on a private network, but they re not routable through the Internet. This is designed for the purpose of creating a measure of well-needed security, but it also conveniently saves valuable IP address space. If every host on every network was required to have real routable IP addresses, we would have run out of IP addresses to hand out years ago. But by using private IP addresses, ISPs, corporations, and home users only need a relatively tiny group of bona fide IP addresses to connect their networks to the Internet. This is economical because they can use private IP addresses on their inside networks and get along just fine. 34

35 Network Address & Broadcast Address Network Address : IP Address with all bits as ZERO in the host portion. Ex: Broadcast Address: IP Address with all bits as ONES in the host portion. Ex: Valid IP Addresses lie between the network address and broadcast address. Only Valid IP addresses are assigned to hosts /clients. Example 1: IP Address: IP Address: Class: A Octet format N.H.H.H Network Address: Broadcast Address: First Address: Last Address : Host Address: Subnet Mask: Example 2: Class : Network Address: Broadcast Address: First Address: Last Address : Host Address: Subnet Mask: 35

36 Types of Addresses Data is transmitted to and from hosts on networks using one of three transmission types: 1-Unicast Most network traffic is unicast in nature, meaning that traffic travels from a single source device to a single destination device. 2-Broadcast Broadcast traffic travels from a single source to all destinations on a network. 3-Multicast Multicast technology provides an efficient mechanism for a single host to send traffic to multiple, yet specific, destinations. 36

37 Subnetting Creating multiple networks from a single network by converting host bits into network bits. Subnetting provides better performance and security. Rules for Subnetting 1-How many subnets? 2x = number of subnets. x is the number of masked bits, or the 1s. (Given SM Default SM) 2-How many hosts per subnet? 2y 2 = number of hosts per subnet. y is the number of unmasked bits, or the 0s. (32- Given SM ). 3-What are the valid subnets? 256 subnet mask = block size, Start counting at zero in blocks size until you reach the subnet mask value. 4-What s the broadcast address for each subnet? The number right before the value of the next subnet. (Broadcast = Next Subnet -1 ) 5-What are the valid hosts? Valid hosts address are the numbers between the subnets and broadcasts address. (First Host = Subnet + 1, and Last Host = Broadcast -1). Subnetting Example 1: Example : IP Address /25 Answer: Network Address: , Subnet Mask: Answer for Five Questions: 1. How many subnets? Since 128 is 1 bit on ( ), the answer would be 2 1 = 2. (25-24=1) 37

38 2. How many hosts per subnet? We have 7 host bits off ( ), so the equation would be = 126 hosts. (32-25=7) 3. What are the valid subnets? = 128. Remember, we ll start at zero and count in our block size, so our subnets are 0, What s the broadcast address for each subnet?. For the zero subnet, the next subnet is 128, so the broadcast of the 0 subnet is 127. Broadcast for the last subnet is always What are the valid hosts? These are the numbers between the subnet and broadcast address. Subnet First Host Last Host Broadcast Subnetting Example 2: Example : IP Address /26 Answer: Network Address: , Subnet Mask: Answer for Five Questions: 1. How many subnets? Since 192 is 2 bits on ( ), the answer would be 2 2 = 4 subnets. (26-24=2) 2. How many hosts per subnet? We have 6 host bits off ( ), so the equation would be = 62 hosts. (32-26=6) 38

39 3. What are the valid subnets? = 64. start at zero and count in our block size, so our subnets are 0, 64, 128, and What s the broadcast address for each subnet? The number right before the value of the next subnet is all host bits turned on and equals the broadcast address. For the zero subnet, the next subnet is 64, so the broadcast address for the zero subnet is What are the valid hosts? These are the numbers between the subnet and broadcast address. Subnet First Host Last Host Broadcast Subnetting Example 3: Example : IP Address /27 Answer: Network address = Subnet mask = Five Questions: 1. How many subnets? 2 3 = How many hosts per subnet? equation would be = 30 hosts. 39

40 3. What are the valid subnets? = 32. We just start at zero and count to the subnet mask value in blocks (increments) of 32: 0, 32, 64, 96, 128, 160, 192, and What s the broadcast address for each subnet (always the number right before the next subnet)?. 5. What are the valid hosts (the numbers between the subnet number and the broadcast address)?. Ethernet Networking The genesis of Ethernet was 1972, when this technology was developed by Xerox Corporation. The original intent was to create a technology to allow computers to connect with laser printers. Ethernet is a contention-based media access method that allows all hosts on a network to share the same link s bandwidth. Some reasons it s so popular are that Ethernet is really pretty simple to implement and it makes troubleshooting fairly straightforward as well. Ethernet is so readily scalable, meaning that it eases the process of integrating new technologies into an existing network infrastructure, like upgrading from Fast Ethernet to Gigabit Ethernet. Ethernet uses both Data Link and Physical layer specifications. 40

41 Carrier Sense Multiple Access Collision Detect (CSMA/CD) Ethernet networking uses a protocol called Carrier Sense Multiple Access with Collision Detection (CSMA/CD), which helps devices share the bandwidth evenly while preventing two devices from transmitting simultaneously on the same network medium. CSMA/CD was actually created to overcome the problem of the collisions that occur when packets are transmitted from different nodes at the same time. When a collision occurs on an Ethernet LAN, the following happens: 1. A jam signal informs all devices that a collision occurred. 2. The collision invokes a random backoff algorithm. 3. Each device on the Ethernet segment stops transmitting for a short time until its backoff timer expires. 4. All hosts have equal priority to transmit after the timers have expired. 41

42 Half-Duplex and Full-Duplex Ethernet Half-Duplex: Data can be sent both ways but only one way at a time. The Ethtent hub can work in Half-Duplex speed mode. Full-Duplex: In full-duplex mode a device can simultaneously send and receive at the same time. The Ethenet switch can work in both Half-Duplex and Full-Duplex modes. 42

43 Current Ethernet Tehcnology Table below offers a listing of multiple Ethernet standards, along with their media type, bandwidth capacity, and distance limitation. Ethernet Cabling There are 3 types of cableing confiuuration used in Ethernet networks: Straight-through cable Crossover cable Rolled cable Straight-through Cable The straight-through cable is used to connect the following devices: Host to switch or hub Router to switch or hub Four wires are used in straight-through cable to connect Ethernet devices. 43

44 Crossover Cable The crossover cable can be used to connect the following devices: Switch to switch Hub to hub Host to host Hub to switch Router direct to host Router to router The same four wires used in the straight-through cable are used in this cable we just connect different pins together. 44

45 Rolled Cable Rolled Ethernet cable is used to connect a host EIA-TIA 232 interface to a router or a switch console serial communication (COM) port. 45

46 Introduction to Cisco IOS The Cisco Internetworking Operating System (IOS) is a proprietary operating system that provides routing, switching, internetworking, and telecommunications features. It runs on most Cisco routers as well as Cisco switches. You can access the Cisco IOS through the console port of a router, from a modem into the auxiliary (or aux) port, or even through Telnet and Secure Shell (SSH). Access to the IOS command line is called an exec session. Setup Mode If the router has no initial configuration, you will be prompted to use setup mode to establish an initial configuration. You can also enter setup mode at any time from the command line by typing the command setup from something called privileged mode. Setup mode covers only some global commands and is generally just not helpful. Here is an example: 46

47 Command-line Interface (CLI) Mode Setup provides a minimum amount of configuration in an easy format for someone who does not understand how to configure a Cisco router from the command line. You always use the command-line interface (CLI) to configure cisco routers or switches by issuing commands. One key to navigating the CLI is to always be aware of which router configuration mode you are currently in.you can tell which configuration mode you are in by watching the CLI prompt. Mode Definition Example User EXEC mode Limited to basic monitoring commands Router> Privileged EXEC mode Provides access to all other router commands Router# Global configuration Commands that affect the mode entire system Router(config)# Once you understand the different modes, you will need to be able to move from one mode to another within the CLI. The commands in table bloew allow you to navigate between the assorted CLI modes: Command Router>enable Meaning Changes from user EXEC to privileged EXEC mode 47

48 Router#disable Router#config term Router(config)#exit Router(config)#interface Changes to user EXEC from privileged EXEC mode Changes to global configuration mode from privileged mode Exits from any configuration mode to privileged mode Enters interface configuration mode from global configuration mode Editing and Help Features The CLI also provides extensive Editing and online help as shown in the table below. Command Meaning Ctrl+P or Up arrow Shows last command entered Ctrl+N or Down arrow Shows previous commands entered Ctrl+Z Ends configuration mode Tab Finishes typing a command for you Router#? Shows all available commands Router#c? Shows all available commands beginning with the letter c Router#clock? Shows all available options for the clock command 48

49 The Internal Components of a Cisco Router and Switch ROM -contains bootstrap program which searches & loads the OS. -It is similar to BIOS of PC. Flash RAM -stores the Internetworking Operating System (IOS). NVRAM -It is similar to hard disk & stores the startup configuration. RAM -It is called main memory & stores the running configuration. Configuring a Router Using CLI A brand new router doesn't have any configuration so initial configuration has to be done first. The following configuration needs to be done: Hostname. IP address. Passwords: 1-Console. 2-VTY (Telnet). 3-Enable or Secret. Save the configurations. Configuring Router s Hostname You can set the identity of the router with the hostname command. This is only locally significant, which means it has no bearing on how the router performs name lookups or works on the internetwork. 49

50 To configure the host name of the router, run the following commands: Router>enable Router#configure terminal Router(config)#hostname HawlerRouter HawlerRouter(config)#exit HawlerRouter(config)# Configuring Router interfaces Interface configuration is one of the most important router configurations, because without interfaces, a router is pretty much a completely useless object. Plus, interface configurations must be totally precise to enable communication with other devices. Network layer addresses, media type, bandwidth, and other administrator commands are all used to configure an interface. To configure IP address to LAN interfaces, run the commands: HawlerRouter >enable HawlerRouter #configure terminal HawlerRouter (config)#interface fastethernet 0/0 HawlerRouter (config-if)#ip address HawlerRouter (config-if)#no shutdown HawlerRouter (config-if)#exit HawlerRouter (config)#exit HawlerRouter # 50

51 Configuring Router s Passwords There are four passwords you ll need to secure your Cisco routers: console, telnet (VTY), enable password, and enable secret. The enable secret and enable password are the ones used to set the password for securing privileged mode. Once the enable commands are set, users will be prompted for a password. The other three are used to configure a password when user mode is accessed through the console port, through the auxiliary port, or via Telnet. To configure an encrypted privileged password, run the following commands: HawlerRouter >enable HawlerRouter #configure terminal HawlerRouter (config)#enable HawlerRouter (config)#exit HawlerRouter # To configure the console password, run the following commands: HawlerRouter >enable HawlerRouter #configure terminal HawlerRouter (config)#line console 0 HawlerRouter HawlerRouter (config-line)#login HawlerRouter (config-line)#exit HawlerRouter (config)#exit HawlerRouter # 51

52 To configure a password for the VTY lines, run the following commands: HawlerRouter >enable HawlerRouter #configure terminal HawlerRouter (config-line)#line vty 0 4 HawlerRouter HawlerRouter (config-line)#login HawlerRouter (config-line)#exit HawlerRouter (config)#exit HawlerRouter # Viewing, Saving, and Erasing Configurations Once you have gone to all the work of creating a configuration, you will need to know how to save it, and maybe even delete configuration. Command Meaning Router#copy run startup Saves the running configuration to NVRAM Router#show run Shows the running configuration Router#show startup Shows the start-up configuration Router#erase startup Erases the configuration stored in NVRAM Router#reload Restart the router Router#show ip interface shows the IP configuration on all interfaces. This command provides a quick overview of Router#show ip interface the router s interfaces, including the logical brief address and status. 52

53 Routing Process The process of moving packets from one network to another network using routers.routers by defualt know only directly connected networks and indirectly connected network must be added to the router either manually by hand (statically) or dynmiacaly via routing protocols. Types of Routing 1. Static Routing. 2. Dynamic Routing. Static Routing In static routing routes for each destination network has to be manually configured by the administrator. Static routing requires destination network ID for configuration therefore used in small network. Dynamic Routing protocols are used to find networks and update routing tables on routers so it requires directly connected network IDs for configuration. dynmiac routing used in medium and large network. 53