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Guide to TCP/IP, Third Edition

Guide to TCP/IP, Third Edition. Chapter 2: IP Addressing and Related Topics. Objectives. Understand IP addressing, anatomy and structures, and addresses from a computer’s point of view

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Guide to TCP/IP, Third Edition

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  1. Guide to TCP/IP, Third Edition Chapter 2: IP Addressing and Related Topics

  2. Objectives • Understand IP addressing, anatomy and structures, and addresses from a computer’s point of view • Recognize and describe the various IP address classes from A to E, and explain how they’re composed and used • Understand the nature of IP address limitations, and how techniques like Classless Inter-Domain Routing and Network Address Translation ease those limitations IP Addressing and Related Topics

  3. Objectives (continued) • Define the terms subnet and supernet, and apply your knowledge of how subnets and supernets work to solve specific network design problems • Understand how public and private Internet addresses are assigned, how to obtain them, and how to use them properly • Recognize the importance and value of an IP addressing scheme IP Addressing and Related Topics

  4. IP Addressing Basics • Computers deal with network addresses as bit patterns • IP uses a three-part addressing scheme • Symbolic • Example “support.dell.com” • Logical numeric • Example 172.16.1.10 • Physical numeric • Six-byte numeric address, burned into firmware (on a chip) by network interface manufacturers IP Addressing and Related Topics

  5. IP Addressing Basics (continued) • Address Resolution Protocol (ARP) • Permits computers to translate numeric IP addresses to MAC layer addresses • ReverseARP (RARP) • Translates MAC layer addresses into numeric IP addresses IP Addressing and Related Topics

  6. Anatomy of an IP Address • IP addresses • Dotted decimal notation • Take the form n.n.n.n, where n is guaranteed to be between 0 and 255 • Each number is an 8-bit number called an octet • Duplication is not allowed IP Addressing and Related Topics

  7. IP Address Classes • IP addresses • Subdivided into five classes: Class A to Class E • For first three classes octets are divided as follows • Class A n. h.h.h • Class B n.n. h.h • Class C n.n.n. h • n = network, h = host IP Addressing and Related Topics

  8. IP Address Classes (continued) • Address Classes D and E are for special uses • Class D addresses • Multicast communications • Class E addresses • Reserved entirely for experimental use IP Addressing and Related Topics

  9. More About Class A Addresses • Class A addresses in binary form • 0bbbbbbb.bbbbbbbb.bbbbbbbb.bbbbbbbb • b can be 1s or 0s • Reserved for special uses • Addresses consisting of all 0s and all 1s • Reserved for private network use • Address for network 10 (00001010) • Reserved for loopbacktesting • Address 127.n.n.n IP Addressing and Related Topics

  10. IP Addressing and Related Topics

  11. More About Class B Addresses • Class B addresses take the following binary form • 10bbbbbb.bbbbbbbb.bbbbbbbb.bbbbbbbb • b can be 1s or 0s • 214 – 2 • Maximum number of usable network addresses • 16,366 • Maximum number of public IP addresses IP Addressing and Related Topics

  12. IP Addressing and Related Topics

  13. More About Class C Addresses • Class C addresses take the following binary form • 110bbbbb.bbbbbbbb.bbbbbbbb.bbbbbbbb • b can be 1s or 0s • 221 – 2 • The maximum number of usable network addresses • Reserved for private use • 256 Class C addresses, from 192.168.0.0 to 192.168.255.255 IP Addressing and Related Topics

  14. IP Addressing and Related Topics

  15. More About Address Classes D and E • Class D addresses • 1110bbbb.bbbbbbbb.bbbbbbbb.bbbbbbbb • b can be 1s or 0s • Multicast addresses • Class E addresses • 11110bbb.bbbbbbbb.bbbbbbbb.bbbbbbbb • b can be 1s or 0s • Only for experimental purposes IP Addressing and Related Topics

  16. Network, Broadcast, Multicast, and Other Special IP Addresses • Network address • Any IP address where all host bits are “0” • Broadcast address • Address that all hosts on a network must read • Broadcast traffic • Seldom forwarded from one physical network to another IP Addressing and Related Topics

  17. Broadcast Packet Structures • IP broadcast packets have two destination address fields • Data Link layer destination address field • Destination network address field IP Addressing and Related Topics

  18. IP Addressing and Related Topics

  19. Multicast Packet and Address Structures • IP gateway • Router or other device that will forward traffic to the host’s physical network • The Internet Corporation for Assigned Names and Numbers (ICANN) • Allocates multicast addresses on a controlled basis IP Addressing and Related Topics

  20. IP Addressing and Related Topics

  21. IP Addressing and Related Topics

  22. The Vanishing IP Address Space • Address space saving techniques • Classless Inter-Domain Routing (CIDR) • Trade in existing IP network addresses • RFC 1918 • Reserves three ranges of IP addresses for private use • Network Address Translation (NAT) • Lets networks use private IP addresses internally and maps them to public IP address externally IP Addressing and Related Topics

  23. Understanding Basic Binary Arithmetic • Four binary calculations must be mastered • Converting binary to decimal • Converting decimal to binary • Understanding how setting increasing numbers of high-order bits to 1 in eight-bit binary numbers corresponds to specific decimal numbers • Understanding how setting increasing low-order bits to 1 in eight-bit binary numbers corresponds to specific decimal numbers IP Addressing and Related Topics

  24. Converting Decimal to Binary • Converting decimal number 125 to binary 125 divided by 2 equals 62, remainder 1 62 divided by 2 equals 31, remainder 0 31 divided by 2 equals 15, remainder 1 15 divided by 2 equals 7, remainder 1 7 divided by 2 equals 3, remainder 1 3 divided by 2 equals 1, remainder 1 1 divided by 2 equals 0, remainder 1 IP Addressing and Related Topics

  25. Converting Binary to Decimal • Count the total number of digits in the number • Subtract 1 from the total (8 - 1 = 7) • Convert to exponential notation, using all the digits as multipliers • 11011011converts as follows • 11011011 = 1*27+1*26+0*25+1*24+1*23+0*22+1*21+1*20 = 128+64+0+16+8+0+2+1 = 219 IP Addressing and Related Topics

  26. High-Order Bit Patterns Binary Decimal 10000000 128 11000000 192 11100000 224 11110000 240 11111000 248 11111100 252 11111110 254 11111111 255 IP Addressing and Related Topics

  27. Low-Order Bit Patterns Binary Decimal Exponent 00000001 1 21 - 1 00000011 3 22 - 1 00000111 7 23 - 1 00001111 15 24 - 1 00011111 31 25 - 1 00111111 63 26 - 1 01111111 127 27 - 1 11111111 255 28 - 1 IP Addressing and Related Topics

  28. IP Networks, Subnets, And Masks • Subnet mask • Special bit pattern that “blocks off ” the network portion of an IP address with an all-ones pattern • Default masks for Classes A, B, and C Class Layout Default Mask Class A n h.h.h 255.0.0.0 Class B n.n h.h 255.255.0.0 Class C n.n.n h 255.255.255.0 IP Addressing and Related Topics

  29. IP Subnets and Supernets • Subnetting • Stealing (borrowing) bits from the host portion to further subdivide the network portion of an address • Supernetting • Stealing bits from network portion • Using them to create a single, larger contiguous address space for host addresses IP Addressing and Related Topics

  30. Calculating Subnet Masks • Types of subnet masking techniques • Constant-length subnet masking (CLSM) • Variable-length subnet masking (VLSM) • In a VLSM addressing scheme • Different subnets may have different extended network prefixes IP Addressing and Related Topics

  31. Designing a Constant-Length Subnet Mask • Decide how many subnets are needed • Add 2 to number of subnets needed then jump to the nearest higher power of two • Reserve bits of host portion’s address from the top down • Be sure that there are enough host addresses left over on each subnet to be usable • If using RIP • Use the formula 2b – 2 to calculate the number of usable subnets from a mask IP Addressing and Related Topics

  32. Designing a Variable-Length Subnet Mask • Analyze requirements for individual subnets • Aggregate requirements by their relationships to the nearest power of two • Use subnets that require largest number of devices • To decide the minimum size of the subnet mask • Aggregate subnets that require fewer of hosts • Define VLSM scheme that • Provides the necessary number of subnets of each size to fit its intended use best IP Addressing and Related Topics

  33. Calculating Supernets • Supernets • “Steal” bits from network portion of an IP address to “lend” those bits to the host • Permit multiple IP network addresses to be combined • Allow an entire group of hosts to be reached through a single router address IP Addressing and Related Topics

  34. Classless Inter-Domain Routing • Limitations • Network addresses must be contiguous • When address aggregation occurs • CIDR address blocks work best when they come in sets that are greater than 1 and equal to some lower-order bit pattern that corresponds to all 1s • Addresses commonly applied to Class C addresses • To use a CIDR address on any network • Routers in routing domain must “understand” CIDR notation IP Addressing and Related Topics

  35. Public Versus Private IP Addresses • Private IP addresses ranges • May be in the form of IP network addresses • Address masquerading • May be performed by boundary devices that include proxy server capabilities • Private IP address limitation • Some IP services require a secure end-to-end connection IP Addressing and Related Topics

  36. IP Addressing and Related Topics

  37. Public Versus Private IP Addresses (continued) • Public IP addresses • Remain important for identifying all servers or services that must be accessible to the Internet • Most organizations need public IP addresses only for two classes of equipment • Devices that permit organizations to attach networks to the Internet • Servers designed to be accessible to the Internet IP Addressing and Related Topics

  38. Managing Access To IP Address Information • Reverse proxying • Permits the proxy server to front for servers inside the boundary • Important service that proxy server provides • Manages what source addresses appear in outbound packets that pass through it IP Addressing and Related Topics

  39. Obtaining Public IP Addresses • Public IP addresses • Issued by ISPs • IP renumbering • Switching addresses on every machine that uses address from old ISP to unique address obtained from new ISP • ICANN • Manages all IP-related addresses, protocol numbers, and well-known port addresses • Assigns MAC layer addresses for use in network interfaces IP Addressing and Related Topics

  40. IP Addressing Schemes • IP addressing scheme constraints • Number of physical locations • Number of network devices at each location • Amount of broadcast traffic at each location • Availability of IP addresses • Delay caused by routing from one network to another IP Addressing and Related Topics

  41. The Network Space • Application Specific Integrated Circuits (ASICs) • Hardware used by switches to make decisions • Layer-3 switch • Implements the layer-3 logic from the software into its own ASICs • Allows you to partition a large network into many smaller subnets with almost no loss of performance IP Addressing and Related Topics

  42. The Host Space • Reasons for using binary boundaries • You may want to implement layer-3 switching to reduce the broadcast traffic • One day you will want to classify your traffic to apply Quality of Service (QoS) or policies of some sort • Can be applied to firewall rules IP Addressing and Related Topics

  43. Summary • IP addresses • Provide foundation for identifying individual network interfaces on TCP/IP networks • IP addresses • Come in five classes named through E • Understanding binary arithmetic • Essential to knowing how to deal with IP addresses IP Addressing and Related Topics

  44. Summary (continued) • Classless Inter-Domain Routing (CIDR) • Permits network-host boundary to fall away from octet boundaries • Subnetting • Permits additional bits to be taken from the host portion of a network • Address masquerading and address substitution • Techniques used to hide internal network IP addresses from outside view IP Addressing and Related Topics

  45. Summary (continued) • Within the Class A, B, and C IP address ranges • IETF has reserved private IP addresses or address ranges • Internet Corporation For Assigned Names and Numbers (ICANN) • Ultimate authority for obtaining public IP addresses IP Addressing and Related Topics

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