1. Classifying Network Addressing
Constructing Network Addresses
Classifying Network Addressing
© 2004 Cisco Systems, Inc. All rights reserved.

2. Outline Overview IP Addressing IP Address Structure IP Address Classes
Reserved IP Addresses
Public and Private IP Addresses
IPv4 vs. IPv6
Summary
Quiz

3. Network and Host Addresses
IP Address is a hierarchical address and consists of 2 parts:
Network address portion (Network ID)
Host address component (Host ID)
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4. Dotted Decimal Notation
IP address is a hierarchical address and consist of 2 parts:
>Network address portion (network ID)
>Host address component (host ID)
An IP address is a 32-bit binary number:
The 32-bit binary number can be divided into four octets:
Each octet (or byte) can be represented in decimal:
The address can be written in dotted-decimal notation:
The 32-bits number represents the network and the remaining bits represent the host.
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5. IP Address Classes
*Class D addresses are used for multicast groups. There is no need to allocate octets or bits to separate network and host addresses.
**Class E addresses are reserved for research use only.
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6. IP Address Class Components
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N = Network number assigned by ARIN
H = Host number assigned by administrator

7. IP Address Range
Class A Extremely large network, 16, available host address.
Class B Large network, 16,384 networks,each supporting more then 65,000 hosts.
Class C small networks, more than 2 million networks,each supporting up to 256 host.
*127 ( ) is a Class A address reserved for loopback testing and cannot be assigned to a network. ( )

8. Network Addresses
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9. Broadcast Address
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10. Public IP Addresses

11. Private IP Addresses
When a network using private address must connect to the Internet, it is necessary to translate the private address to a public addresses. This translation process is called NAT. A router is often the network device that perform NAT.

12. IPv4 Address Allocation
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13. IPv4 and IPv6 8*4=32 bits 8*16=128 bits Lesson Aim
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8*16=128 bits

14. Summary
IP network addresses consist of two parts: the network portion and the host portion.
IPv4 addresses have 32 bits that are divided into octets and are generally shown in dotted decimal form (for example, ).
IPv4 addresses are divided primarily into A, B, and C classes. Other classes (D and E) exist, but they are reserved for special uses (multicasting and research).
When written in a binary format, the first bit of a Class A address is always 0, the first 2 bits of a Class B address are always 10, and the first 3 bits of a Class C address are always 110.

15. Summary (Cont.)
Certain IP addresses (network and broadcast) are reserved and cannot be assigned to individual network devices.
Internet hosts require a unique, public IP address, but private hosts can have any valid private address that is unique within the private network.
Addressing space as defined by IPv4 is limited and has been mostly exhausted.
The more flexible IPv6 will replace IPv4 in the future. IPv6 offers 128 bits of addressing compared to the 32-bit addressing available in IPv4.