VLSM and CIDR

Objectives

• Compare and contrast classful and classless IP addressing.
• Review VLSM and explain the benefits of classless IP addressing.
• Describe the role of the Classless Inter-Domain Routing (CIDR) standard in making efficient use of scarce IPv4 addresses

Introduction

• Prior to 1981, IP addresses used only the first 8 bits to specify the network portion of the address
• In 1981, RFC 791 modified the IPv4 32-bit address to allow for three different classes
IP address space was depleting rapidly the Internet Engineering Task Force (IETF) introduced Classless Inter-Domain Routing (CIDR)

- CIDR uses Variable Length Subnet Masking (VLSM) to help conserve address space.
-VLSM is simply subnetting a subnet

Classful and Classless IP Addressing

• Classful IP addressing
• As of January 2007, there are over 433 million hosts on internet
• Initiatives to conserve IPv4 address space include:

-VLSM & CIDR notation (1993, RFC 1519)
-Network Address Translation (1994, RFC 1631)
-Private Addressing (1996, RFC 1918)

Next, please download the links Below
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http://www.ziddu.com/download/14538265/20091022_Chpater6Overview.pdf.html

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