Addressing the Network – IPv4

© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 1Version 4.0

Addressing the Network – IPv4

Network Fundamentals – Chapter 6

2© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public

Objectives Explain the structure IP addressing and demonstrate the ability

to convert between 8-bit binary and decimal numbers. Given an IPv4 address, classify by type and describe how it is

used in the network. Explain how addresses are assigned to networks by ISPs and

within networks by administrators. Determine the network portion of the host address and explain

the role of the subnet mask in dividing networks. Given IPv4 addressing information and design criteria, calculate

the appropriate addressing components. Use common testing utilities to verify and test network

connectivity and operational status of the IP protocol stack on a host.


IP Addressing Structure Inside the devices, digital logic is applied for

interpretation of the address Human – 32 bits is difficult to interpret + remember Represented as dotted decimal


IP Addressing Structure


IP Addressing Structure Converting 8-bit binary to decimal


IP Addressing Structure Converting 8-bit binary to decimal


IP Addressing Structure Converting 32 bits IP Address




IP Addressing Structure Converting 32 bits IP Addresses




IP Addressing Structure Converting 32 bits IP Address Exercise 00001011?


IP Addressing Structure Decimal to 8-bit binary








IP Addressing Structure Converting decimal to 8-bit binary- practice


Addressing Types of Communication

In IPv4 network, the hosts can communicate in one of three different ways



Unicast Most common in CS and P2P



Broadcast Using Broadcast Address Two types:

Directed Broadcast – Broadcast is sent to all hosts on a specific network/nonlocal Limited Broadcast - Broadcast is sent to all hosts on local network



Multicast Only to selected set of hosts




IPv4 Addresses Three types of addresses in the network:

• Network address: A special address that refers to the network• Cannot be assign to a device, only reference to a network• The lowest address in IPv4 address range

• Broadcast address: A special address used to send data to all hosts in the network• The highest address in IPv4 address range

• Host addresses: The unicast addresses assigned to the end devices in the network


IPv4 Addresses


IPv4 AddressesNetwork prefix When an IPv4 network address is expressed, a prefix

length added to the network address. This prefix length is the number of bits in the address

that gives the network portion. Written in slash format. That is a forward slash (/)

followed by the number of network bits. Example, in 172.16.4.0 /24, the /24 is the prefix length. This tells you that the first 24 bits are the network

address. The remaining 8 bits, the last octet, are the host portion.


IPv4 AddressesNetwork prefix Network not always assigned a /24 prefix Depends on the number of hosts on the network

28=256, 27=128…


IPv4 Addresses Determine the network, broadcast and host addresses

for a given address and prefix combination172.16.4.35/24

Type of Address Last octet in binary

Last octet in decimal

Full address in decimal

Network 00000000 0 172.16.4.0

Broadcast 11111111 255 172.16.4.255

First Useable Host Address

00000001 1 172.16.4.1

Last Useable Host Address

11111110 254 172.16.4.254


IPv4 Addresses Exercise Determine the network, broadcast and host addresses

for a given address and prefix combination

144.83.250.97/25

Type of Address Last octet in binary

Last octet in decimal

Full address in decimal

Network

Broadcast

First Useable Host Address

Last Useable Host Address


Public address and Private address Although most IPv4 host addresses are public

addresses designated for use in networks that are accessible on the Internet, there are blocks of addresses used in networks that require limited or no Internet access.

These addresses are called private addresses. The private address blocks are

■ 10.0.0.0 /8 (10.0.0.0 to 10.255.255.255)

■ 172.16.0.0 /12 (172.16.0.0 to 172.31.255.255)

■ 192.168.0.0 /16 (192.168.0.0 to 192.168.255.255) Private space address blocks are set aside for use in

private networks.


Public address and Private address Private space address blocks are set aside for use in

private networks. Packets using these addresses as the source or

destination should not appear on the public Internet The router or firewall device at the perimeter of these

private networks must block or translate these addresses

These services, called Network Address Translation (NAT), can be implemented on a device at the edge of the private network. NAT changes the private space addresses in the IPv4 packet header to a public space address


Public address and Private address


Purpose of several special addresses Default route

• The IPv4 default route is 0.0.0.0. This default route is a “catch all” route to route packets when a more specific route is not available.

• 0.0.0.0 /8 address block (0.0.0.0–0.255.255.255).

Loopback address• The loopback address use to direct traffic to themselves. • Shortcut method for TCP/IP applications and services that run

on the same device to communicate with one another. • Two services on the same host can bypass the lower layers of

the TCP/IP stack. • 127.0.0.1 address is used, address block 127.0.0.0 /8

(127.0.0.0 to 127.255.255.255) is reserved.


Purpose of several special addresses• ■ Link-local address

• 169.254.0.0 /16 address blocks (169.254.0.0 to 169.254.255.255)

• can be automatically assigned to the local host by the operating system in environments where no IP configuration is available.

• only suitable for communication with other devices connected to the same network

■ Test-net addresses• set aside for teaching and learning purposes.• block 192.0.2.0 /24 (192.0.2.0 to 192.0.2.255)• used in documentation and network examples.


TBC

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Addressing the Network – IPv4