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

2. Objectives
Describe IP addressing, anatomy and structures, and addresses from a computer’s point of view
Recognize and describe IPv4 addressing and address classes, describe the nature of IPv4 address limitations, and define the terms subnet, supernet, subnetting, and supernetting
Describe how to obtain public and private Internet addresses
Explore IPv4 addressing schemes
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3. Objectives (cont'd.)
Describe the nature of IPv4 address limitations and why IPv6 is needed
Discuss new and enhanced IPv6 features
Recognize and describe IPv6 addressing schemes, features, and capacities
Describe the impediments involved in transitioning from IPv4 to IPv6
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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
Physical numeric
Six-byte numeric address, burned into firmware (on a chip) by network interface manufacturers
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5. IP Addressing Basics (cont'd.)
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
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6. IPv4 Addressing Numeric IPv4 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
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7. IPv4 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
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8. IP Address Classes (cont'd.)
Address Classes D and E are for special uses
Class D addresses
Multicast communications
Class E addresses
Reserved entirely for experimental use
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9. Network, Broadcast, Multicast, and Other Special IPv4 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
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10. Broadcast Packet Structures
IPv4 broadcast packets have two destination address fields
Data Link layer destination address field
Destination network address field
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12. Broadcast Packet Structures (cont’d.)
Multicast Packet and Address Structures
Host listens on the multicast and broadcast addresses besides its own
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
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14. Broadcast Packet Structures (cont’d.)
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15. IPv4 Networks and Subnets 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
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16. IPv4 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
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17. IPv4 Subnets and Supernets (cont’d.)
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
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18. IPv4 Subnets and Supernets (cont’d.)
Bitcricket IP Calculator
Free subnet mask calculator from WildPackets
First to support IPv6
Classless Inter-Domain Routing (CIDR) routes can also be calculated
SolarWinds IP Subnet Calculator
Provides address details such as reverse DNS resolution and response time
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19. Classless Inter-Domain Routing in IPv4
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
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20. Public Versus Private IPv4 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
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21. Public Versus Private IPv4 Addresses (cont’d.)
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22. Public Versus Private IPv4 Addresses (cont'd.)
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
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23. Managing Access To IPv4 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
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24. Obtaining 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
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25. IPv4 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
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26. 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
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27. 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
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28. The End of the IPv4 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
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29. Introducing IPv6
IPv6
Provides a vast abundance of IP addresses and better management of its address space
Eliminates the need for NAT
Has modernized routing support and natively allows for expansion along with the growing Internet
Supports network security by using authentication and encryption extension headers
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30. Request for Comments Pages and Depreciation
Request for Comments (RFC)
Describe the methods, innovations, and standards that are applied to every aspect of the Internet, including IPv6
RFC 5156
Contains a summary of various other RFCs regarding special usage of IPv6 addresses
When reviewing RFCs
Make special note of depreciated and obsolete information and documents
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31. IPv6 Addressing IPv6 addresses 128 bits long
String that uniquely identifies one single network interface on the global Internet
Contains a network portion and a host portion
Network and host portion depend on who’s looking at it and where they are located
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32. Address Format and Notation
Addresses in IPv6 are also binary numbers
Expressed using hexadecimal notation (00–FF)
Broken up differently
IPv6 uses groups of four 16-bit numbers called “words,” separated by a colon character (:)
Examples:
1090:0000:0000:0000:0009:0900:210D:325F or
1090::9:900:210D:325F
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33. Network and Host Address Portions
Network prefix similar to CIDR
Examples:
1090::9:900:210D:325F / 60
1018:FD0C:0:9:90:900:10BB:A / 24
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34. Scope Identifier 4-bit field
Limits the valid range for a multicast address
Defines the portion of the Internet to which the multicast group pertains
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35. Interface Identifiers
IPv6 requires that every network interface have its own unique identifier
Hardware vendors tend to use the modified EUI-64 format
Software makers, including Microsoft, use the privacy format defined in RFC 4941
Having the right-hand portion of your IPv6 address based on the computer’s MAC or hardware address presents a security concern
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36. Interface Identifiers (cont’d.)
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37. Native IPv6 Addresses in URLs
RFC 2732 (originally proposed in 1999)
Describes a method to express IPv6 addresses in a form compatible with HTTP URLs
Uses square brackets ([ and ]), to enclose a literal IPv6 address
Example:
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38. Address Types Special addresses Multicast addresses Anycast address
Unspecified address
All zeroes and can be represented as two colon characters (::) in normal notation
Loopback allows a host on a network to check the operation of its own local TCP/IP protocol stack
Multicast addresses
Used to send an identical message to multiple hosts
Anycast address
Packets addressed to an anycast address go to the nearest single instance of that address
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39. Address Types (cont’d.)
Unicast address
Sent to one network interface
Aggregatable global unicast address
Can be combined with other addresses into a single entry in the router table
Link-local address
First 10 (leftmost) bits set to
Site-local address
First 10 (leftmost) bits set to
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40. Address Allocations
IPv6 pre-allocates only about 15 percent of its available addresses
Network Service Access Point (NSAP) addressing
Holds 1/128 of all the IPv6 address space
Unicast and anycast allocations
Multicast allocations
All IPv6 addresses beginning with 0xFF
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42. IPv6 Addressing and Subnetting Considerations
In general IPv6 does not require subnetting
Although possible
Extent to which you can “subnet” an IPv6 address depends on the length of the prefix
How you apportion the host addressing depends on the prefix length
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43. The IPv4 to IPv6 Transition
Transition technologies:
Teredo tunneling
ISATAP or Intra-Site Automatic Tunnel Addressing Protocol
6to4 tunneling
NAT-PT (Network Address Translation-Protocol Translation)
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44. Summary IP addresses IPv4 addresses
Provide foundation for identifying individual network interfaces on TCP/IP networks
IPv4 addresses
Come in five classes named through E
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
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45. Summary (cont'd.) Address masquerading and address substitution
Techniques used to hide internal network IP addresses from outside view
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
The world has all but run out of IPv4 addresses
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46. Summary (cont'd.)
IPv6 introduces a number of improvements and updates to the IP protocol
IPv6 supports three address types: unicast, multicast, and anycast
IPv6 employs two private or local-use address schemes
IPv6 prefix lengths define the number of bits apportioned to the network address and to the host address
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