Module 4.0 - Planning the Addressing Structure 4.0 - Chapter Introduction 4.0.1 - Introduction Single Diagram Diagram 1. Slideshow As small-to-medium-sized business networks expand to meet the challenges of new applications and services, they often outgrow their initial design. A key factor when planning the network upgrade is network addressing. Creating a flexible, scalable IP addressing structure able to support new growth is critical to the success of the upgraded network. Today, there are millions of individuals connected to this global network and the number is growing. After completion of this chapter, you should be able to: Describe how IP addressing is implemented in the LAN. Subnet a given network to allow for efficient use of IP address space. Explain how Network Address Translation (NAT) and Port Address (PAT) are used in a network. 4.1 - IP Addressing in the LAN 4.1.1 - Review of IP Addresses Four Diagrams Diagram 1, Animation Diagram shows how an IP address gets expressed in dotted decimal notation. An IP Address is a 32-bit logical network address 32 bits are difficult to read so we split them into 4 octets convert to base 10 and separate the numbers with dots. We call this dotted-decimal notation Diagram 2, Animation IP addresses are hierarchical A hierarchy is like a family tree with parents at the top and offspring, or children, connected to them. In a network hierarchy, the network is similar to the parent and the hosts represent the children. In this example, the network is identified by the first three octets and the host by the fourth octet. Diagram 3, Image Class A - The first octet denotes the network address, and the last three are the host portion. Any IP address where the first bit of the first octet is 0 is a Class A. Class A addresses can have a decimal value within the first octet ranging between 1 and 126. These address are typically used for networks with more than 65,534 hosts. The Class A address 127 is reserved for loopback testing. Class B - The first two octets denote the network address, and the last two are the host portion. Any IP address where the first two bits of the first octet are 10 is a Class B. Class B addresses can have a decimal value within the first octet ranging between 128 and 191. These addresses are typically used for networks that have between 255 and 65534 hosts. Class C - The first three octets denote the network address, and the last one is the host portion. Any IP address where the first three bits of the first octet are 110 is a Class C. Class C addresses can have a decimal value within the first octet ranging between 192 and 223. These address are typically used for networks with 254 or less hosts. Class D - Used for multicast addressing. Any IP address where the first four bits of the first octet are 1110 is a Class D. Class D addresses can have a decimal value between 224 and 239. Class E - Reserved for future experimental usage and broadcasting. Any IP address where the first five bits of the first octet are 11110 is a Class E. Class E addresses can have a decimal value between 240 and 255. Diagram 4, Table IP Address Classes A Class has a first octet range of 1-127 or 00000000-01111111, a decimal subnet of 255.0.0.0, a possible 126 networks, 16777214 hosts and is used for commercial purposes. B Class has a first octet range of 128-191 or 10000000-10111111, a decimal subnet of 255.255.0.0, a possible 16382 networks, 65534 hosts and is used for commercial purposes. C Class has a first octet range of 192-223 or 11000000-11011111, a decimal subnet of 255.255.255.0, a possible 2097150 networks, 254 hosts and is used for commercial purposes. D Class has a first octet range of 224-239 or 11100000-11101111, and is reserved for multicast purposes. E Class has a first octet range of 240-255 or 11110000-11110111, and is reserved for experimental purposes. 4.1.2 - Subnetting a Network Two Diagrams Diagram 1, Table Illustrates how the network is separated into subnets. Diagram 2, Table and Image Illustrates the use of private IP Addresses Class A - 10.0.0.0 to 10.255.255.255 has a subnet mask of 255.0.0.0 can have 1 network, 16777214 hosts. Class B ? 172.16.0.0 to 172.31.255.255, a subnet mask of 255.255.0.0, 16 networks, 65534 hosts per network and 1048544 Total hosts. Class C ? 192.168.0.0 to 192.168.255.255, a subnet mask of 255.255.255.0, 256 Networks, 254 hosts per network and 65024 otal hosts. 4.1.3 Classful Subnetting Two Diagrams Diagram 1, Animation Illustrates the IP address hierarchy of network, subnets and hosts. Diagram 2, Animation Illustrates how the IP address hierarchy can be divided for classful subnetting. 192.168.1. 0 11000000 10101000 00000001 hhhhhhhh 0 Subnet ID Bits 8 Host ID Bits 1 Number of Subnets 254 Number of Hosts hhhhhhhh Bit pattern Subnet ID bits = 0, the network has one subnet. 1 Subnet ID Bits 7 Host ID Bits 2 Number of Subnets 126 Number of Hosts s hhhhhhh Bit pattern As soon as one of the host bits is designated as a subnet bit, the network will have two subnets. Remember, in binary, a bit can have two states, 1 or 0, so the number of subnets is 2^s. 2 Subnet ID Bits 6 Host ID Bits 4 Number of Subnets 62 Number of Hosts ss hhhhhh Bit pattern 3 Subnet ID Bits 5 Host ID Bits 8 Number of Subnets 30 Number of Hosts sss hhhhh Bit pattern 4 Subnet ID Bits 4 Host ID Bits 16 Number of Subnets 14 Number of Hosts ssss hhhh Bit pattern Notice the inverse relationship between the number of subnets and the number of hosts. 5 Subnet ID Bits 3 Host ID Bits 32 Number of Subnets 6 Number of Hosts sssss hhh Bit pattern Our example network has fewer than six hosts in it. If we had to really subnet this network, would we choose to break it into two subnets, or would we choose to break it into the number of subnets that support 6 hosts? 6 Subnet ID Bits 2 Host ID Bits 64 Number of Subnets 2 Number of Hosts ssssss hh Bit pattern 4.1.4 - Custom Subnet Masks Three Diagrams Diagram 1, Slideshow Illustrates a representation of the addressing scheme. Diagram 2, Slideshow Illustrates a representation of the addressing scheme. Diagram 3, Slideshow Illustrates a representation of the addressing scheme. 4.1.5 Communicating Between Subnets Three Diagrams Diagram 1, Animation Illustrates how router interfaces are to be included in the subnets. Diagram 2, Image Packet Tracer Exploration: Communicating Between Subnets Diagram 3. Image Lab Activity Subnetting a Network 4.1.6 IPv6 Two Diagrams Diagram 1, Timeline Timeline ? Evolution of IP from IPv4 to IPv6 1981 RFC 791 defined(IPv4) 1993 RFC 1519 defined CIDR 1996 RFC 1918 defined private IP addressing 1998 RFC 2460 defined IPv6 1998 to Present ? transition from IPv4 to IPv6 (ongoing) Diagram 2, Animation IPv6 addresses are 128 bits long. 4.2 - NAT and PAT 4.2.1 - Basic Network Address Translation (NAT) Two Diagrams Diagram 1, Animation What is NAT and Why Do WE Need It? Company Web and Mail Server NAT is required between the local private network and the public Internet. Network Address Translation allows many users in a private network to use a few public IP addresses. Diagram 2, Table Advantages of NAT are public IP address sharing, Transparent to end users, Improved Security, LAN expandability or scalability, Local control including ISP connectivity. Disadvantages of NAT are, Incompatibility with certain applications, Hinders legitimate remote access, Performance reduction caused by increased router processing. 4.2.2 - IP NAT Terms Two Diagrams Diagram 1, Animation Illustrates the process by which NAT translates private IP addresses. The gateway router translates the private IP address to a public IP address from the NAT address pool, before sending it on the outside network. When the remote server replies, it uses the translated address as the destination address of the packet. The gateway router receives the packet and translates the destination address back to the inside private address. Diagram 2, Activity Match the NAT address terminology to the source and destination of the datagram. Match the Inside and Outside options to the correct Address Type. Remember, devices from the LAN are inside. On the inside network, IP addresses are local. On the outside network, IP addresses are global. A) Inside Local B) Outside Local C) Inside Global D) Outside Global ISP 1) Source, translated IP Address 2) Destination, 209.165.200.226 LAN 3) Source, 192.168.1.106 4) 209.165.200.226 4.2.3 ? Static and Dynamic NAT Single Diagram Diagram 1, Animation Inside Local Addresses 192.168.1.106 Outside Global Addresses 209.165.200.226 Static NAT Before translation the permanently assigned IP Adress is 192.168.1.106 and after translation the permanently assigned IP address is 209.165.202.129 Dynamic NAT Any of the IP Addresses on the LAN such as 192.168.1.0 are translated dynamically to anyone of these globally unique IP addresses, 209.165.201.0 / 27 4.2.4.0 - Port-based Network Address Translation (PAT) Three Diagrams Diagram 1, Image Illustrates a local network with 40 private users and 1 public address. The TCP process in the user PC attaches a port number to its source IP address to be included in the outbound request. The destination is a web server, and the destination address has well-known port 80 attached. The gateway router receives the request and translates the source IP address to the one available public IP address. It then picks an available port number from the available ports (any port greater than 1024) and binds it to the public IP address before forwarding the packet. The server responds, sending it to the same IP address and port combination it received it from. The gateway receives the response and recognizes the IP address and port combination and translates the combination to the correct IP address, 192.168.1.106, and binds the original port number to it so that the communications loop can be closed. Diagram 3, Lab Activity Determine the number of port address translations being performed. 4.2.5.0 - IP NAT Issues Single Diagram No meaningful information 4.3.0.0 - Chapter Summary 4.3.1.0 - Summary Slideshow Slide 1 Text * Interfaces on network devices connected to the Internet need to have a unique IP address, to send and receive messages over internetworks. * IP addresses are organized into network classes A, B, C, D, and E, and are conserved by the creation of private IP address space. * A network can be divided into subnets. * Classful subnetting uses the extension of the subnet mask. Classless IP addressing, part of a method called classless inter-domain routing (CIDR) uses a flexible method of subnetting with variable length subnet masks (VLSM). Slide 2 Text * Subnet masks allow further subdivision of networks by extending the number of bits used. * A subnet ID is created by splitting the host ID into two parts, a subnet ID and a new host ID. * The number of bits in the subnet ID determines the number of subnets there can be in a network. * Communication between subnets requires routing. Slide 3 Text * NAT enables a large group of private users to access the Internet by sharing a small pool of public IP addresses, thereby reducing the consumption of globally unique IP addresses. * Inside addresses are IP addresses for private network devices. Outside addresses are IP addresses for public network devices. Local addresses are IP addresses in packets that are still in the private network. Global addresses are IP addresses that cross to the outside network. * A packet that has been translated and is in the outside network will list an inside-global IP address as source and an outside-global IP address as destination. * IPv6 incorporates a 128-bit addressing scheme, whereas IPv4 uses 32-bits. Slide 4 Text * Static NAT is for permanent one-to-one translations from a specific inside-local IP address to a specific inside-global IP address. * Dynamic NAT assigns inside-global IP addresses on a first-come, first-served basis from an available pool of IP addresses to a designated network or sub-network. * PAT, can be used to add a port number to the IP address for specific connections. * Network devices that use NAT translate addresses on every packet. This can significantly increase processing work load. 4.4.0.0 - Chapter Quiz 4.4.1.0 - Quiz Single Diagram Quiz: Planning the Addressing Structure Take the chapter quiz to check your knowledge. Click the quiz icon to begin.