25-08-2017, 09:32 PM
IP Addressing A Simplified Tutorial
IP Addressing A Simplified.pdf (Size: 319.4 KB / Downloads: 101)
INTRODUCTION
The purpose of this tutorial is to give the newcomer to data
networking a basic understanding of IP addressing. The following topics
are covered.
– IP addressing fundamentals
– Classful IP addressing
– Subnet masks
– Variable length subnet masks (VLSM)
– Classless inter-domain routing (CIDR)
– Routing and routing protocols
OSI and TCP/IP
• This table is presented for reference purposes.
– The first column shows the 7-layer OSI Reference Model, which is a model
used to design protocols that make networking possible.
– The second column shows the TCP/IP protocol stack in reference to the OSI
model. TCP/IP is the prevalent protocol stack for data networking.
– The third column shows that an IP address is a layer 3 (L3) address, as well
as its relationship to the MAC address and TCP/UDP port, which are not
covered in this tutorial.
Anatomy of an IP address
• The IP address is a 32-bit address that consists of two components.
• One component is the network portion of the address, consisting of the
network bits.
– The network bits make up the left portion of the address.
– They consist of the first bit up to some boundary, to be discussed later.
• The second component is the host portion of the address, consisting of
the host bits.
– The host bits make up the right portion of the address.
– They consist of the remaining bits not included with the network bits.
The mask
• The network portion of the address is separated from the host portion of
the address by a mask.
• The mask simply indicates how many bits are used for the network
portion, leaving the remaining bits for the host portion.
• A 24-bit mask indicates that the first 24 bits of the address are network
bits, and the remaining 8 bits are host bits.
• A 16-bit mask indicates that the first 16 bits of the address are network
bits, and the remaining 16 bits are host bits.
• And so forth…
• The difference between a network mask and a subnet mask will be
explained as this tutorial progresses.
Dotted decimal notation
• Machines read the IP address as a stream of 32 bits.
• However, for human consumption, the IP address is written in dotted
decimal notation.
– The 32-bit address is divided into 4 groups of 8 bits (an octet or a byte).
– Each octet is written as a decimal number ranging from 0 to 255.
– The decimal numbers are separated by periods, or dots.
Public addresses
• Most IP addresses are public addresses. Public addresses are registered
as belonging to a specific organization.
• Internet Service Providers (ISP) and extremely large organizations in the
U.S. obtain blocks of public addresses from the American Registry for
Internet Numbers (ARIN http://www.arin.net). Other organizations obtain
public addresses from their ISPs.
• There are ARIN counterparts in other parts of the world, and all of these
regional registration authorities are subject to the global Internet Assigned
Numbers Authority (IANA http://www.iana.org).
• Public IP addresses are routed across the Internet, so that hosts with
public addresses may freely communicate with one another globally.
• No organization is permitted use public addresses that are not registered
with that organization!