IP Address
• Internet Structure
– Larger networks
• Subnetwork:
» Hosts
• IP address
-What information
should an IP address
provide?
• Mailing address:
– State
– City
– Street address
• IP address:
– Network address
– Subnet address
– Host address
• IPv4
Example: 4 octets
• Total # of addresses
available 256*256*256*
256= 4,294,967,296!
Problem:
1. Only 256 networks?
2. What if the network only contains several subnets
and less than 10 hosts in each subnet?
• IPv4
Example: 4 octets
• Total # of addresses
available 256*256*256*
256= 4,294,967,296!
Problem:
1. Only 256 networks?
2. What if the network only contains several subnets
and less than 10 hosts in each subnet?
• Solution: classify networks into 3categories:
Class A. Network address : first octet 1~127
examples: 2.32.126.78, 2.21.9.45
Network administrator can assign addresses to their subnets and hosts
using remaining three octets.
Class B. Network address: first octet 128~191 and second octet
examples: 138.92.74.211, 138.92.59.3
Network administrator can assign addresses to their subnets and hosts
using remaining two octets.
Class C. Network address: first octet 192~223 and second, third
examples: 217.168.1.4, 217.168.1.15
Comparison of three types of
networks
Class
First octet
Network
address
Host
address
Number of
networks
Number of
addresses
available for
each network
A
1~127
a
b.c.d
27 = 128
224 = 16,777,216
B
128~191
a.b
c.d
214 = 16,384
216 = 65536
C
192~223
a.b.c
d
221 = 2,097,152
28 = 256
• Are Billions of ip addresses enough for
computers all over the world?
– IPv4 addresses have already been exhausted in
2011!
• IPv6
– 128 bits in length
• IPv4 : 4 octets, each octet has 8 binary bits, total 32 bits
• IPv6: 8 components, each component has 16 binary
bits, total 128 bits.
– Capability: 2128
• Practice 1
– Consider you are a network administrator and you
are monitoring the network communications. You
captured packets from 5 different ip addresses,
identify the faked addresses among them and
classify the rest addresses into three
categories( Class A, Class B ,and Class C).
•
•
•
•
•
102.98.92.1
102.98.261.2
198.136.134
138.69.2.15
192.168.300.2
• Practice 1
– Consider you are a network administrator and you
are monitoring the network communications. You
captured packets from 5 different ip addresses,
identify the faked addresses among them and
classify the rest addresses into three
categories( Class A, Class B ,and Class C).
•
•
•
•
•
102.98.92.1
102.98.261.2 261>255
198.136.134
138.69.2.15
192.168.300.2 300>255
• Practice 1
– Consider you are a network administrator and you
are monitoring the network communications. You
captured packets from 5 different ip addresses,
identify the faked addresses among them and
classify the rest addresses into three
categories( Class A, Class B ,and Class C).
•
•
•
•
•
102.98.92.1class A 102 is among 0-127
102.98.261.2
198.136.134 class C 198 is among 192-223
138.69.2.15 class B 138 is among 128-191
192.168.300.2
• Practice 2
– Providing a Class B network address, assume that
the network administrator has set a subnet with
network addresses ranging from 181.46.12.* to
181.46.16.*. Calculate number of addresses
available in this subnet.
• Practice 2
– Providing a Class B network address, assume that the
network administrator has set a subnet with network
addresses ranging from 181.46.12.* to 181.46.16.*.
Calculate number of addresses available in this subnet.
According to class B ip address format, the first two octets are
fixed in this network,
In each of the subnet segments specified by the third octet,
there are 256 possible addresses,
Example: 181.46.12.0~ 181.46.12.255
181.46.13.0~ 181.46.13.255
#= 256* (16-12+1)=1280 addresses
• Practice 3
– Assuming that you are arranging ip addresses for a
company, the company has 3000 computers.
Choose 1 class from the 3 classes (A, B and C ) for
addressing; based on your choice, give a subnet
range that can guarantee that every computer will
have a valid and unique ip address.
• Practice 3
– Assuming that you are arranging ip addresses for a
company, the company has 3000 computers.
Choose 1 class from the 3 classes (A, B and C ) for
addressing; based on your choice, give a subnet
range that can guarantee that every computer will
have a valid and unique ip address.
• Class B network address: 0~2^16 different addresses
• # of subnet segments required= 3000/256=11.7~=12
• The subnet segments (third octet) can be 0~11 or 9~20
or 210~221 or any 12 numbers with the values
between 0~255.