This unit contains the following two lessons: Lessons Pages Length Lesson 3-1: Network Layer Addressing hours

Transcription

1 Unit 3 Let s Route Overview Description This unit contains two lessons: The first lesson introduces the format for addressing data that travels across the Internet. The lesson focuses on the underlying binary system that determines how addresses are assigned and analyzed. The second lesson introduces the basic functions of routers. It begins with a description of the IP packet format. The lesson focuses on an introduction to routing tables and how static routes can be entered into those tables. The lesson concluded with a brief introduction to dynamic routing. Unit Table of Contents This unit contains the following two lessons: Lessons Pages Length Lesson 3-1: Network Layer Addressing hours Lesson 3-2: Routing hours ST A 97

2 Unit 3: Let s Route Lesson 3-1: Network Layer Addressing At a Glance Layer 3 addresses are commonly called IP addresses because the Internet Protocol is the most common protocol found operating at the Network Layer. IP addresses can identify any machine on any network connected to the Internet, no two machines have the same IP address at the same time. Many networks that are not connected to the Internet also use IP addressing because it is a standard way of allocating addresses. Blocks of IP addresses were originally allocated to various networks. These blocks of addresses came in several sizes, called classes. Large networks then divided the addresses within a class and assigned them to subnetworks. The process of creating subnetworks with a common network address is called subnetting. Addresses are comprised of 32 bits divided into two parts: a network portion and a host portion. The original scheme for IP addresses has required improvement as the Internet has grown. In this lesson, you will learn about the improvements in use, including CIDR. What You Will Learn After completing this lesson, you will be able to do the following: Identify the convention for IP addressing. Identify three classes of IP addresses. Convert IP addresses between binary and dotted decimal notation. Demonstrate how to subnet a Class A, B, or C address into a given number of subnetworks. Determine the subnet mask for a subnetted network. Identify why CIDR is being implemented over classful IP addressing. Configure the router s interface parameters to support IP on a synchronous circuit. Verify that all routers in the lab network are reachable. 98 ST A Routing

3 Lesson 3-1: Network Layer Addressing Tech Talk Classless Interdomain Routing (CIDR) A version of IP addressing that allows IP networks of many sizes instead of just the sizes specified by the IP classes. Dotted decimal notation The standard way of representing IP addresses in decimal form Ipv4 The current standard for IP addressing that uses 32 bits for an address Ipv6 The newer standard for IP addressing that uses 128 bit addresses IP Class A block of IP addresses allocated to a single network. Natural Mask The IP mask that identifies the natural class of an IP address when subnetting is not being used. Octet A set of eight bits. IP addresses are comprised of four octets. Prefix The number of bits in the network portion of a CIDR IP address, like a subnet mask Subnetwork A network that uses a subset of the addresses in an IP Class. Subnet mask A 32 bit pattern of bits that indicates which part of an IP address identifies the network and subnetwork (indicated by 1s in the mask) and which part identifies the specific host on that subnetwork (indicated by the 0s in the mask). Variable Length Subnet Masking (VLSM) A version of subnetting in which a network can be subdivided into subnetworks of various sizes. 99 ST A

4 Unit 3: Let s Route IP Addressing Just as the postal service needs accurate addressing in order to deliver the mail, computer networks need accurate addressing in order to deliver data. The standard form of addressing used for the Internet is called Internet Protocol or IP addressing. A postal address can be broken down into house number, street name, city, state, country and zip code. Similarly, an IP address may be divided into network, subnetwork, and host, represented by 32 bits. A host is any machine on the network that can receive and transmit IP packets. Address notation When surfing the web, web site addresses can be represented in two ways. A uniform resource locator or URL An IP address. The mnemonic name, nortelnetworks.com, is called a domain name, and is easier to remember than the numeric IP address. Whenever a domain name is entered into a web browser, the browser searches a database called a Domain Name Service that tells it how to convert the mnemonic name into the corresponding IP address. Writing the address as four numbers separated by periods is called dotted decimal notation. Dotted decimal notation is another representation of the IP address. The version of the IP address closest to what routers actually use is in binary form, because that is what a computer understands best. Dotted-decimal Notation Represents a Binary Number / / / IP addresses are made of 32 bits written as four sets of eight bits called octets. To a network device looks like this: / / / ST A Routing

5 Lesson 3-1: Network Layer Addressing Converting Between Binary and Decimal Numbers To understand how addresses are assigned and interpreted, it is necessary to work with addresses in binary format. But addresses are usually written in dotted decimal notation. Therefore, it is important to understand how to convert between the formats. Manual Conversion Although conversions may be done on a calculator, the concept of how to translate between binary and decimal using paper and pencil is important to network administrators. A calculator may not always be available when a quick conversion is needed. 1. Each position in a binary octet has a decimal equivalent Position in Octet Decimal Equivalent To calculate the decimal equivalent of a binary octet, multiply the binary number in each position by its decimal equivalent then add the products Binary Number Decimal Equivalent Product Add the sum of products ( =134). 101 ST A

6 Unit 3: Let s Route A shorter way to do the math is to add together the decimal equivalents of all the positions in the octet that have a 1. To convert from decimal to binary, find the highest decimal equivalent of the octet that is less than the decimal number. Place a 1 in that location. Subtract the decimal equivalent from the decimal address and then repeat the process with the remainder. For example, convert 134 to binary: 1. The highest decimal equivalent from the octet that is less than or equal to 134 is 128. Place a one in the 8th position Position in Octet Decimal Equivalent Binary Number =6. The highest decimal equivalent less than or equal to 6 is 4. Place a 1 in the 3 rd position. Position in Octet Decimal Equivalent Binary Number =2. The highest decimal equivalent less than or equal to 2 is 2. Place a 1 in the 2 nd position. Position in Octet Decimal Equivalent Binary Number =0. Once 0 is reached, fill in the empty positions with 0s and the conversion is completed. Position in Octet Decimal Equivalent Binary Number ST A Routing

7 Lesson 3-1: Network Layer Addressing Calculator Conversions Conversion of address notations is easily accomplished using the scientific calculator included as an accessory in Windows. 1. Use the Start menu to find and run the calculator. 2. In the Calculator window, pull down the View menu and select Scientific. 3. At the top left of the window four buttons labeled Hex (Hexadecimal or base 16), Dec (Decimal or base 10), Oct (Octal or base 8), Bin (Binary or base 2) will be displayed. 4. To convert from one numbering system to another, click on the numbering system of the original number then type it in. For example, click on binary and type in a set of eight bits from the example above. Click on the number system desired to convert to. The converted number will display automatically. How Many Addresses? One way to think about how many IP addresses there are, is to compare IP addresses to zip codes. A zip code has five decimal digits. Each digit can be any of ten numbers: 0, 1, 2, 3, 4, 5, 6, 7, 8, or 9. So there are 10*10*10*10*10 or 10 5 possible zip codes or 100,000. This seemed to be plenty when zip codes were first invented but as the population grew, the post office needed more zip codes. When the post office started using zip+4, it added four more digits to each zip code. Now there are 10 9 or 1,000,000,000 possible zip codes. A billion zip codes seems like plenty when considering that is nearly 4 zip codes for every man, woman, and child in the United States. IP addresses use 32 bits, each bit can be any of two numbers: 1 or 0. So there are 2 32 or 4,294,967,296 possible IP addresses. Over four billion addresses seems like plenty when considering that there are about five billion people in the world and many still do not have computers. There is, however, a shortage of Internet addresses. IP Version 6 Just as the post office added four more digits to zip codes, the Internet will, over the next few years, add 96 more bits to IP addresses, making them 128 bits long. The new addressing scheme is called IP version 6 (IPv6) and it will solve many of the problems with the current 32 bit addressing used by IP version 4 (Ipv4). 103 ST A

8 Unit 3: Let s Route Reserved Addresses Certain IP addresses are reserved. They cannot be used by hosts on the Internet. The addresses ( ) and ( ) are both reserved. Addresses with a first octet of (127) are reserved as loop back addresses which refer back to the sender. Check Your Understanding Convert the following addresses into dotted decimal notation: Convert the following addresses into binary: What are two IP addresses that can t be assigned to a host? 104 ST A Routing

9 Lesson 3-1: Network Layer Addressing IP Addressing and Classes There are newer more efficient methods of allocating IP addresses but it is necessary to first understand the original method called classful addressing. Once the Internet committee established the 32-bit addressing scheme, it assigned addresses to all the networks that made up the Internet. Each computer in each network had to have a unique address so that it would not be confused with any other computer in any other network. Some networks were very large with thousands of computers while some were very small. Because most networks tend to grow and add computers, each network wanted addresses for the machines it had at the time, as well as for machines it might add in the future. The committee created classful addressing as a way of dividing the 4.3 billion addresses among the various sizes of networks. Parts of an IP Address 32 Bits Network ID Host ID In classful IP addressing, part of the address corresponds to the network and the remaining part of the address corresponds to a particular host on that network. For example, in the address , stands for the network, while 3.35 stands for the particular host on that network. 105 ST A

10 Unit 3: Let s Route Zip Code Map Classful addressing can be compared to the way the post office uses zip codes. A zip code has nine digits, for example The first digit corresponds to the region of the country. Any mail with a zip code beginning with 0 is destined for the Northeast or New Jersey. Mail with a zip code beginning with 3 is destined for the Southeast. Mail with a zip code starting with 9 is headed for the West Coast or Alaska or Hawaii. When the post office sorts mail, the first sorter only has to look at the first digit of the zip code to determine what part of the country the mail should be sent to. Once the mail gets there, the regional post office looks at the next four digits of the zip code to determine what local post office the mail should be sent to. Once the mail gets to the local post office, the sorter there looks at the last four digits to determine what street or building to which the mail goes. 106 ST A Routing

11 Lesson 3-1: Network Layer Addressing The job of sending data through the Internet is divided among routers. Some routers only send data to the borders of specific networks but not to particular hosts on those networks. These routers only have to remember the part of the address that identifies the network. Routers inside of networks receive data from the outside and then send it to the specific host on the inside. IP Address Classes Binary Address through through through Dotted-decimal Representation Class Reserved through through through Class A addresses Class B addresses Class C addresses Reserved 107 ST A

12 Unit 3: Let s Route Class A addresses Class A addresses were created for the largest networks. Class A addresses use the first octet to indicate the network and the other three octets to indicate hosts on that network. The range of Class A network addresses begins with and end with Class A addresses actually end with but when describing a class address, zero indicates anything between 0 and 255. For example, the Class A address actually means through There is 126 Class A addresses. Each network with a Class A address can have 16,777,214 different host addresses. The Class A address allocation is much larger than most networks would ever really use. No individual network has over 16 million machines. Class A Addresses Class A First Octet Range Example Network Host Class A 0XXXXXXX ST A Routing

13 Lesson 3-1: Network Layer Addressing Class B Addresses Class B addresses are for medium sized networks. They use the first two octets to represent the network address and the last two octets to represent the host address. Class B addresses begin with and end with (again, the zeroes mean any number between 0 and 255). There are 16,382 Class B addresses and each Class B network can have 65,534 different host machines. Class B Addressing Class B First Octet Range Example Network Host Class B 10XXXXXX ST A

14 Unit 3: Let s Route Class C Addresses Class C addresses are for smaller networks. They use the first three octets to represent the network address and the last octet to represent the host address. Class C addresses range from to There are 2,097,150 Class C addresses and each Class C network can have 254 different host machines. Addresses above are used for Class D addresses, which are used for multicasting, and Class E addresses, which are used for research by the Internet committee. Class C Addressing Class C First Octet Range Example Network Host Class C 110XXXXX ST A Routing

15 Lesson 3-1: Network Layer Addressing Reserved Addresses Two of the addresses in any network are reserved. The all 0 address, for example , is reserved as the address of the network itself (in this case the zeroes actually mean 0 and not any number from 0 to 255 ). This is the only address that routers outside the network need to know in order to send packets to that network. The all 1 address, for example , is reserved as the broadcast address for that network. Packets with this address will be received by every device on the network. These two addresses are reserved on all networks, Class A, B, and C, as well as all subnetworks. Natural Masks When a router tries to forward a packet it looks for the portion of the address that identifies the destination network. A mask tells the router which portion of the address it should look at to find the network. Masks are written in binary. Bits set to one indicate the network portion. Bits set to zero indicate the host portion. A Class A address uses the first octet to indicate the network. Its natural mask is written: or A Class B address uses the first two octets to indicate the network. Its natural mask is written: or A Class C address uses the first three octets to indicate the network. Its natural mask is written: or Masks for Class A, B, and C addresses are called natural masks. Check Your Understanding Which of the following is a Class A address? Which of the following is a Class B address? ST A

16 Unit 3: Let s Route Which of the following is a Class C address? Subnetting The Internet is divided into Class A, B, and C networks. Those networks are in turn divided into subnetworks. Network administrators subdivide networks to separate traffic destined for one part of a large network from traffic destined for another part. Administrators use routers to subdivide networks. This is called subnetting. For example, suppose a large telecommunications company has a Class B network with the address: giving it 65,534 possible host addresses. This company has a manufacturing division, a sales division, an administrative division and several other divisions. Data from the manufacturing division includes huge drawing files created by the engineers that take up an enormous amount of bandwidth. To keep the manufacturing division data from slowing down the rest of the network, the network administrator puts that division on its own network, which is really a subnetwork of the Class B. The administrator may also put the sales and administrative divisions on their own subnetworks. Each of these subnetworks is connected to an interface on a router. A Large Network Without a Subnetwork Before Internet Router Sales Sales Manuf g Manuf g Manuf g Admin 112 ST A Routing

17 Lesson 3-1: Network Layer Addressing When an Internet user sends a packet to the company, the first two octets of the address identify the network address. Once the packet arrives at the company Class B network, the router must determine which subnetwork the packet is intended for. The administrator configures the router to interpret part of the host address as a subnetwork address. In the example, the third and fourth octets make up the host address. The administrator can subdivide the host portions of the address to use the third octet as the subnetwork address and the fourth octet as the host address. Now when a packet arrives from the Internet, the router uses the third octet to determine whether the packet is destined for the manufacturing or sales or administrative division and the fourth octet to determine the specific host on the subnetwork for that division. A Large Network Divided into Subnetworks After Internet Router Sales Sales Sales Admin Admin Manuf g Manuf g Manuf g Manuf g 113 ST A

18 Unit 3: Let s Route Subnet Masks When a router with subnetworks receives a packet from the Internet, it uses a subnet mask to determine which portion of the destination address identifies the subnetwork and which part identifies the host on that subnetwork. A subnet mask looks like a natural mask with more of the bits set to one. The additional ones identify the subnetwork address. As with a natural mask, any bit set to zero is part of the host address. Subnet masks are entered into a router using dotted decimal notation. For example, a Class B network has the address The first two octets identify the network. If the administrator uses the entire third octet to identify the subnetwork, then the subnet mask is or A Class C network uses the first three octets to identify the network. The last octet can be subdivided so that some of the bits identify a subnet of the Class C and the rest identify the host. Subnetting Network Portion Internet Subnet Portion Host Portion ST A Routing

19 Lesson 3-1: Network Layer Addressing Subnetting Tradeoffs Just as a Class A, B, or C network has a specific number of possible host addresses, each subnetwork also has a specific number of possible host addresses. Out of 32 total bits in a Class B address, 16 (the third and fourth octets) are available to identify a host. There are 2 16 or 65,536 possible host addresses within the Class B. Two of these addresses, the one ending with all ones and the one ending with all zeroes, are reserved. So there are 65,534 possible host addresses. If an administrator uses the third octet to identify the subnetwork then there can be 2 8 or 256 subnetworks, but two subnets are not used ( and ), so the subnetworks available is or 254 subnetworks. Each of those subnetworks can have or 254 possible host addresses. Subnetting a Class B using 8 bits Class B address space: Subnet mask: Network Subnetwork Host Dotted Decimal Notation reserved subnets = 254 possible subnetworks, reserved=254 possible hosts per subnetwork 115 ST A

20 Unit 3: Let s Route To create fewer subnetworks with more hosts per subnetwork, it is possible to use fewer bits to identify the subnetwork address, leaving more bits available for the host address. For example, the administrator can choose to use only four of the bits in the third octet for the subnetwork address. Four bits remain in the third octet plus the eight bits in the fourth octet for the host address. This yields 2 4 or 16 subnetworks, but two are reserved or not recognized by most routers (0000 and 1111) which leaves only 14 possible subnets and (2 12 ) or 4,054 possible host addresses on each subnetwork. Subnetting a Class B using 4 bits Class B address space: Subnet mask: Network Subnetwork Host Dotted Decimal Notation reserved subnets = 14 possible subnetworks 4054 Hosts possible 116 ST A Routing

21 Lesson 3-1: Network Layer Addressing Subnetting Restrictions At least two bits must be used to identify a subnetwork. If there were only one bit to define the subnetwork address, there would be only two possible subnetworks, 1 and 0. But both of those addresses are reserved. This leaves no possible subnetworks. There must always be two bits left for the host address. If there were only one bit to define the host addresses in a subnetwork, there would be only two possible host addresses, 1 and 0. But both of those addresses are reserved. This leaves no possible hosts. When a network is subdivided, two addresses are reserved for each subnetwork addresses. This leaves fewer addresses available for hosts. Check Your Understanding In any subnetwork, which two addresses cannot be assigned to a host? What is the purpose of subnetting? 117 ST A

22 Unit 3: Let s Route Complete the following table: Subnetting a Class C Address Number of bits used to identify subnetwork Subnet Mask in binary and in dotted decimal notation Number of useable subnetwork addresses Number of useable host addresses in each subnetwork or How would you divide the Class C address into 28 subnetworks? Hint: You may not be able to get 28 networks exactly. How many hosts would each Class C subnetwork be able to accommodate? What would the subnet mask look like for any of the Class C subnetworks. Give the answer in binary and in dotted decimal notation. 118 ST A Routing

23 Lesson 3-1: Network Layer Addressing Variable Length Subnet Masking (VLSM) The original scheme for IP addresses and subnetting has required improvement. As networks grow, network administrators need to use their IP addresses more efficiently, they can no longer afford to let addresses go unused. When an IP class address is divided into subnetworks using a subnet mask, every subnetwork created has the same number of possible host addresses. A company might not want to divide its network into equalsized subnetworks. It might have a manufacturing division with 50 people, a sales division with 20 people, and an administrative division with 3 executives who like to keep all their data private. If the company has a Class C network address, it would have to choose between subnetting into 2 networks of 62 hosts or 6 networks of 30 hosts. The first choice would force the company to leave the Sales and Administrative divisions on a single network. It would also limit the Manufacturing division to adding a maximum of 12 more hosts. The second choice would force the manufacturing division to use two subnetworks. It would also waste 23 host addresses in the Administrative division s subnet. Variable Length Subnet Masking (VLSM) offers a solution to the problems of subnetting. VLSM allows a different subnet mask to be used for each subnetwork. This means that there can be different sizes of subnetworks within a single network. Classless Internet Domain Routing Classes A, B, and C provided only three choices for networks: 65,777,214 hosts, 65,534 hosts, or 254 hosts. If a company had 500 people, it could use several Class C networks and have to route between several domains just within the company. Or, the company could use a Class B address and waste approximately 65,000 possible addresses. Classless Internet Domain Routing (CIDR) does away with Internet classes altogether. It is the addressing method used in the Internet today, though some older networks still use subnetting as described above. Each CIDR address has its own mask called a prefix. Like a subnet mask, the CIDR prefix tells how many bits of the CIDR address represent the network address and how many represent the host address. Actually, the prefix only tells how many bits are used for the network portion and the router or other network device assumes that the remaining bits are the host portion. Because the traditional IP address classes are not used in CIDR, there are many more possible network sizes. When writing a CIDR address, you must add a slash and the prefix to the 119 ST A

24 Unit 3: Let s Route end of the address. For example, a CIDR address of /20 indicates a prefix of 20 bits. That is, the first 20 bits of the address indicate the network. Internet Protocol Version 6 Internet Protocol version 6 (IPv6) is the long-term solution to the problems of Internet Addressing. IPv6 uses 128 bit addresses instead of 32 bit used by IPv4. Check Your Understanding What does the following address notation indicate? /26 Write the CIDR mask for the above address in binary. How many possible hosts could there be in the above CIDR network? 120 ST A Routing

25 Lesson 3-1: Network Layer Addressing Try It Out Introduction to Site Manager Site Manager is an SNMP application that communicates with the router using UDP/IP. SNMP operates at the IP application layer, which sends data to UDP at the transport layer, which sends data to IP at the network layer. This means that for Site Manager to run on a PC connected to a router, the PC must have the IP protocol stack installed (or at least the UDP and IP portions), and the router must have at least one port configured to accept IP packets. This is why TI is used to configure the first port on the router. Materials Needed: Nortel Networks' Advanced Remote Node (ARN) Router Classroom Network Windows 95 PC Site Manager Nortel Networks V.35 Serial Cable (Model # 7835, Part # A) Any Word Processor (e.g., MS Word) (optional) Pen/Pencil and Paper Student Portfolio In this lab you will learn how to: Use Site Manager. Configure the router s interface parameters to support IP on a synchronous circuit. Verify that all routers in the lab network are reachable. Part One: Starting Site Manager and Use Site Manager to Configure the Router 1. With your PC connected (through the LAN) to the router, start Site Manager. 2. If the Router Connections Options window opens, type the IP Address of the configured router port. This window will not display if Site Manager already knows the IP address from a previous session. The 121 ST A

26 Unit 3: Let s Route main Site Manager window will display the known routers and their communications status as up or down. The Router Connection Options window also displays three other pieces of information: Identity: works essentially like a password You can specify a name that must be typed in to access the router. Actually this is a very weak form of security. A network administrator who wants to prevent unauthorized changes to a router s configuration will need to use additional security measures. Timeout How long Site Manager will wait for the router to respond to a command before it issues the command again. Retries (per request) The number of times Site Manager will issue a command when the router does not respond. This introductory activity uses two options from the Tools menu: Configuration Manager Used to create and edit configuration files Statistics Manager Used to view router status In this activity, you will configure a WAN connection as a synchronous circuit. The terms WAN connection and synchronous connection are used interchangeably. Site Manager will be used to configure the port. 1. To use the Configuration Manager in remote mode: a. Click Tools. b. Click Configuration Manager. c. Click Remote File. Configuration Manager allows the creation of a configuration file in four different modes: Local Mode Create a configuration file and save it on your PC, then transfer it to the router for later use Remote Mode Create a configuration file and save it on the router, then use it to start the router later Dynamic Mode Change the configurations of the router as you work. Cache Mode Configuration changes go directly to the router s active memory (DRAM)_and a copy is made locally on the Site Manager PC. 122 ST A Routing

27 Lesson 3-1: Network Layer Addressing 2. When the Edit Remote Configuration File window opens, locate the startup.cfg configuration file in the Directory box. If the startup.cfg file is not displayed in the directory box, it may be necessary to select a different volume within the Volume box. a. Locate the file startup.cfg. b. Click the file to select it. c. Click Open. d. The startup.cfg file is transferred (via tftp) from the router s memory (the flash card) to the PC. The file is copied into C:\WF\CONFIG. If a file named startup.cfg already exists in C:\WF\CONFIG, you will be prompted whether you want to back up the file. Select No, so that the file from the router memory overwrites the file already on the PC. e. Site Manager opens and displays the file startup.cfg it just received. 3. Enter system information for the router. a. Choose a system name for each router. In the remainder of this activity, the routers in the network will be referred to as Router A and Router B. b. Choose more interesting names, perhaps after cities in distant parts of the world, to simulate a long distance between the two routers. c. To keep the names straight, put a sign on each router with its name. d. Click Platform. e. Click Edit. f. Click System Information. g. When the Edit System Description Parameters window opens, enter the router s System Name, System Contact, and System Location. h. Click OK. 123 ST A

28 Unit 3: Let s Route Part Two: Configuring a Synchronous Circuit Layers 1 and 2 are defined for a particular circuit when the router is configured. If the circuit is a LAN, Site Manager automatically defines the Layer 1 and 2 characteristics when a particular connector on the router is chosen. If the circuit is a WAN, it is necessary to specify the type of WAN protocol to be used. 1. From the Configuration Manager window, click Circuits. 2. Click Add Circuit. The Add Circuit window displays a blank box for the Circuit Name. The default circuit name consists of an abbreviation for the type of connection followed by two numbers that identify the circuit location on the router. The options for circuit types are: E Ethernet E1 E1 F fiber distributed data interface (FDDI) H high-speed serial interface (HSSI) MCE1 Multichannel E1 (MCE1) MCT1 Multichannel T1 (MCT1) O token ring S synchronous T1 T1 3. On the Add Circuit screen: a. Click the synchronous interface (for example, COM1) that will be configured as a WAN circuit b. In the Circuit Name box, change the name of the synchronous connection. Name the connection for the router that it connects to. For example, S12_RouterB would be the synchronous port on Router A that connects to Router B. c. Click OK. A pop-up list will appear with a list of choices for WAN protocols. For this first configuration, a proprietary protocol for Nortel Networks routers will be used. This protocol is a version of PPP designed especially for one Nortel Networks router to talk to another Nortel Networks router. All router manufacturers include their own protocols as well as such widely used WAN protocols as Frame Relay and ATM. 124 ST A Routing

29 Lesson 3-1: Network Layer Addressing 4. Choose Standard as the WAN protocol. 5. Click OK. 7. Enable both IP and IP/RIP on this circuit. 8. Click OK. 9. On the Select Protocols window, click the IP and RIP boxes. 10. Click Ok. 11. Refer to the network topology diagram and assign the correct IP address and subnet mask for this circuit. 12. Leave the Transmit Broadcast parameter at its default setting. 13. Click OK to return to the main Configuration Manager screen. Part Three: Saving the Configuration File 1. In the Nortel Networks Configuration Manager window, click File. 2. Click Save As. 3. When the Save Configuration File window opens, do the following: a. In the Enter File Name box, enter the name of the router just configured with the extension.cfg. For example, RouterA.cfg. b. Click Save. c. If the message specified file already exists, do you want to overwrite appears, click Yes. d. The configuration file is saved onto the PC in C:\WF\CONFIG. e. When the File Saved message appears, click OK. f. The configuration file still needs to be transferred (via tftp) to the Flash memory on the router. 4. In the Nortel Networks Configuration Manager window, select Tools, Routers File Manager From the Routers File Manager window select the "file", "tftp", "put files" option. A window appears with the local hard drive of your computer set to the "c:\" prompt, change to the directory where you just saved to "C:\WF\Config" and then select the configuration file, click "add" and then ST A

30 Unit 3: Let s Route click "okay" your configuration file will be transferred to the router using tftp. 6. A status window will appear with the file transfer progress and it will be updated when the transfer is complete.(the progress update window may flash onto your screen and disappear as the file your transferring is so small, a larger file like arn.exe will take much longer) 7. Exit File Manager 8. In the Nortel Networks Configuration Manager window, select File. 9. Click Exit. 10. Start Technicians Interface (TI). 11. Log in as Manager. 12. Type dir to make sure the file is now stored in the router s memory. 13. Check to see if the same configuration file is on the PC under C:\WF\CONFIG. 14. Connect your router to your neighbors router according to the lab network map using the V.35 serial cable, make sure that Com 1 of your router is connected to Com 1 of your neighbors router. 15. Boot the router using the new configuration file, Boot arn.exe (your router name).cfg. 16. When the router has finished booting: a. Exit Technicians Interface. b. Return to Site Manager. c. On the main menu screen, select the router from the Well-Known Connections list. d. Be sure that the router s information is displayed. e. Repeat the above exercise for each Com port on your router connecting to another router in the lab network, check with your instructor for the proper IP addressing for each router interface Part Four: Verifying That All Circuits are Operational 1. Return to the Site Manager main menu screen. 2. Click Tools 126 ST A Routing

31 Lesson 3-1: Network Layer Addressing 3. Click Statistics Manager. 4. Click Tools. 5. Click Screen Manager. When the Screen Manager appears, note the default Nortel Networks statistics screens in the upper left corner. Screen Manager allows the addition of any of the default statistics screens to the Current Screen List. Only the screens that are in the Current Screen List may be launched (viewed). 6. Find each of the following default screens and add it to the Current Screen List by selecting it and clicking Add. a. IP_MAIN2.DAT b. IP_TRFC2.DAT c. T_SYNC.DAT 7. Click OK to confirm that the screens are added. 8. Return to the Statistics Manager screen. 9. From the Statistics Manager screen, launch and view a screen that will verify that the circuits you have configured are working. a. Click Tool. b. Click Launch. c. In the Statistics Launch Facility window, select and launch the IP_TRFC2.DAT screen. d. View the IP_TRFC2.DAT screen to see the state of the router s circuits. 10. From the Statistics Manager screen, launch and view a screen that will verify that traffic is being sent at the line level. a. Click Tools. b. Click Launch. c. In the Statistics Launch Facility window, select and launch the T_SYNC.DAT screen. d. Is there traffic moving in and out? 127 ST A

32 Unit 3: Let s Route 11. From the Statistics Manager screen, launch and view the IP_MAIN2.DAT screen. If it appears that all circuits are operational, go on to the next step. If not, try to troubleshoot. Part Five: Compare using Site Manager to Technicians Interface. 1. Return to Technician s Interface. 2. Use the TI show and monitor commands to check the operational status of circuits. Are there any advantages to using TI rather than Site Manager? 3. Now that a protocol has been loaded into several slots, use the TI commands that show information about protocols. a. Type show system protocols. b. Type loadmap. 4. Ping the Ethernet interface of each router. If any router is unreachable, try to resolve the problem. (Hint: Use the p qualifier) 5. When all ports on all routers are reachable from any PC on any port, the exercise is complete. The router s interface has been configured using Site Manager. 6. Include any notes or reactions to this activity in your portfolio. Rubric: Suggested Evaluation Criteria and Weightings Criteria % Your Score Following specific instructions 30 Demonstrate an understanding of configuration details Successful troubleshooting and problem resolution techniques TOTAL ST A Routing

33 Lesson 3-1: Network Layer Addressing Stretch Yourself CIDR Materials Needed: Classroom Network Any Word Processor (e.g., MS Word) (optional) Pen/Pencil and Paper 1. Set up a 26-bit CIDR addressing scheme for the class network. 2. Draw a new network diagram correctly indicating the addresses of all devices in both binary and dotted decimal notation. 3. Exchange your diagram with another member of the class and check his or her work. Rubric: Suggested Evaluation Criteria and Weightings Criteria % Your Score Devise CIDR addressing scheme 50 Correctly drawn diagram 30 Check partner s work 20 TOTAL ST A

34 Unit 3: Let s Route Network Wizards Teaching Binary Math Materials Needed: Pen/Pencil and Paper Student Portfolio 1. Write a 30-minute lesson to teach 8 th graders how to convert between binary and decimal numbers. The lesson should be engaging and clear. 2. Create a rubric to evaluate the lesson s effectiveness. 3. Present your lesson to the class. 4. Participate in an open critique of the lesson, entertaining changes that would improve the lesson. 5. Based on the class critique, complete the lesson s rubric. Rubric: Suggested Evaluation Criteria and Weightings Criteria % Your Score Clear and engaging lesson which meets the time restraints. 40 Appropriate rubric created and completed. 20 Presentation of lesson and participation in class critique. 40 TOTAL ST A Routing

35 Lesson 3-1: Network Layer Addressing Summary In this lesson, you learned the following: The convention for IP addressing. Three classes of IP addresses. How to convert IP addresses between binary and dotted decimal notation. How to subnet a Class A, B, or C address into a given number of subnetworks. How to determine the subnet mask for a subnetted network. Why CIDR is being implemented over classful IP addressing. How to configure the router s interface parameters to support IP on a synchronous circuit. How to verify that all routers in the lab network are reachable. Review Questions Name Lesson 3-1: Network Layer Addressing Part A 1. IP addresses are specified by a a. 28-bit number b. subnet mask c. 32-bit number d. single octet e. 8 octets 2. Which of the following is a valid IP address for a workstation? a b c ST A

36 Unit 3: Let s Route d e Every computer that is connected to the Internet has a. The same IP address b. At least 3 IP addresses c. The same IP address as the main router on its local network d. A unique IP address e. A unique AppleTalk ID 4. Some portion to the left of an IP address indicates a. The workstation address within a network b. The number of computers in the local network c. The size of the network d. The address of the network Part BAnswer: d 132 ST A Routing

37 Lesson 3-1: Network Layer Addressing Part B 1. A class A IP address has a. 24 bits available for local addresses b. 64 bits available for local addresses c. 8 bits available for local addresses d. 24 bits fixed for the network address 2. A class B address has a. 24 bits available for local addresses b. 16 bits fixed for the network address c. 8 bits available for local addresses d. 8 bits fixed for the network address 3. A class C address has a. 8 bits fixed for the network address b. 16 bits fixed for the network address c. 24 bits available for the local addresses d. 8 bits available for local addresses Part C 1. Convert into binary notation 2. Convert to dotted decimal notation Part D 133 ST A

38 Unit 3: Let s Route 1. Subnet the class B network into 8 subnets. Part E 1. What are the host address ranges and subnet masks for each subnet in a class C network ( ) that has been subnetted into 16 equal subnets? Part F 1. Class-based IP addressing a. Provides flexible network sizes b. Only offers three sizes of network address spaces c. Uses a variable length mask for each domain d. Controls the suffix of each network s domain name 2. Classless Internet Domain Routing (CIDR) allows a. Domains to choose one of three network sizes b. Domains to have several names c. Domains to have an address mask length appropriate to the desired network size d. Have more then four octets in their dotted decimal address Scoring Rubric: Suggested Evaluation Criteria and Weightings Criteria % Your Score Part A: Identify the convention for IP 20 dd i 134 ST A Routing

39 Lesson 3-1: Network Layer Addressing addressing. Part B: Identify three classes of IP addresses. 20 Part C: Convert IP addresses between binary and dotted decimal notation. Part D: Demonstrate how to subnet a Class A, B, or C address into a given number of subnetworks. Part E: Determine the subnet mask for a subnetted network. Part F: Identify why CIDR is being implemented over classful IP addressing TOTAL 100 Try It Out: Configure the router s interface parameters to support IP on a synchronous circuit. Verify that all routers in the lab network are reachable. 100 Stretch Yourself 100 Network Wizards 100 FINAL TOTAL 400 Resources Bay Networks. (1999). Accelerated Router Configuration, Bay Networks, Inc., Billerica, Massachusetts. Bay Networks. (1998). Installing and Operating BayStack ARN Routers, Bay Networks, Inc., Billerica, Massachusetts. Palmer, M. (1998) Hands on Networking Essentials with Projects, Course Technology, Cambridge, Massachusetts. 135 ST A

40 Unit 3: Let s Route 136 ST A Routing