Internet Protocol Address
Kittipong Warasup
kittipong@sit.kmutt.ac.th
What we will learn
Internet Protocol Address 2
What is an IP address?
IP address is requires for each host on a TCP/IP
internetwork.
To access other devices on the network.
To network component.
To manage the device.
The IP address must be unique across the entire
internetwork.
Internet Assigned Number Authority (IANA) is in
charge of how IP addresses are assigned.
Internet Protocol Address 3
Duplicate IP Address
The second host with the duplicate IP address
has its IP stack disabled.
A warning message is issued to both host.
Both host continue to use the same IP address.
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IP Address Representation
There are two form
Binary representation
Dotted-decimal Notation
On a single network segment, all hosts share the same
network prefix, but must have a unique host number.
On different network segment, hosts have different
network prefixes, but may have the same host number.
Network Number Host Number
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Binary Representation
Each IP address is a stream of 32 1s and 0s.
11000000101010000111100011111111
We only work with up to eight digits.
The largest value allowed for an octet is
11111111 which is 255 in decimal.
The lowest value allowed for an octet is
00000000 which is 0.
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Dotted-Decimal Notation
An IP address comprises four octets which make
up the 32-bit address.
Octets are written in decimal notation and
separated using dot between each other.
Bit# 0 31
11000000 . 10101000 . 01111000 . 01100100
192 . 168 . 120 . 100
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IP Address Classes
There are five pools of IP addresses designated as classes
of IP addresses.
Each of the first three classes of IP addresses is composed
of a network and host portion of those IDs.
Class A Net Host Host Host
Class B Net Net Host Host
Class C Net Net Net Host
Class D Multicast
Class E Reserved
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Class A Address
Class A network address has an 8-bit network
prefix and 24-bit host number.
The highest order bit set to 0.
The rest 7-bit of first octet creates unique
network ID.
The last three octets left for the host ID.
0
Network Number 24-bit Host Number
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Class B Address
Class B network address has an 16-bit network
prefix and 16-bit host number.
The two highest order bit set to 10.
The rest 6-bit of first octet and the next octet
create unique network ID.
The last two octets left for the host ID.
1 0
Network Number 16-bit Host Number
Internet Protocol Address 10
Class C Address
Class C network address has an 24-bit network
prefix and 8-bit host number.
The three highest order bit set to 110.
The rest 5-bit of first octet and the next two
octets create unique network ID.
Only the last octet left for the host ID.
1 1 0
Network Number 24-bit Host Number
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Class D Address
Class D addresses are reserved for multicast
group, not assigned to individual hosts.
The four highest order bit set to 1110.
First octet of Class D value between 224 and 239.
The remaining 28 bits represent the multicast
group.
1 1 1 0
24-bit Multicast Group
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Class E Addresses
Class E addresses are experimental addresses,
not available to the public.
They have been reserved for future use.
The four highest order bit set to 1111.
First octet of Class E value between 240 and 255.
1 1 1 1 0
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Special IP Addresses
Some IP addresses have been reserved and cannot be assigned to
individual hosts.
IP addresses with the host ID set to all 0s represent a network
address.
IP addresses with the host ID set to all 1s represent a network’s
broadcast.
The network address 127 is reserved for loopback functions.
Class Network Address Broadcast Address Example
A x.0.0.0 x.255.255.255 125.0.0.0, 125.255.255.255
B x.y.0.0 x.y.255.255 131.1.0.0, 131.255.255.255
C x.y.z.0 x.y.z.255 202.1.1.0, 202.255.255.255
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Local Network Address
Three pools of IP addresses have been reserved for use on local
network.
10.0.0.0 through 10.255.255.255
172.16.0.0 through 172.31.255.255
192.168.0.0 through 192.168.255.255
These IP addresses are not in use on the internet.
They only can be used behind firewalls and proxy servers that hide
them from the internet.
202.44.8.40
Interne
t
Firewall/
External Network Proxy Server
Internal Network
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IP Address Class Summary
IP High – Address Number of
Purpose Bits Network/
Address Format Order Range Max. Hosts
Class Bit (s) Host
Few large
A N.H.H.H 0 1.0.0.0 to 16,777,214
Organizations 7/24
126.0.0.0 (224-2)
B N.N.H.H Medium - size
1,0 128.1 to 65,543
Organizations 14/16
191.254.0.0 (216-2)
C N.N.N.H Relatively
1,1,0 192.0.1.0 to
Small 22/8
223.255. 254(28-2)
Organizations
254.0
Not for
D - Multicast commercial
224.0.0.0 to
Groups (RFC use
1,1,1,0 239.255.255 -
1112)
E - 240.0.0 to -
Experimental 254.255.
1,1,1,1 -
255.255
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Subnet Masks
Subnet masks designate which bits of an IP
address represent the network portion and which
bits represent the host portion.
Default subnet masks are:
Class A is 255.0.0.0
Class B is 255.255.0.0
Class C is 255.255.255.0
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The ANDing Process
When two hosts attempts to communicate with each other, the
source uses its subnet mask to determine whether the destination is
on the local network or a remote network.
192.168.1.20
255.255.255.0
192.168.1.10
255.255.255.0
Host A’s IP address 11000000 10101000 00000001 00001010
Host A’s subnet mask 11111111 11111111 11111111 00000000
ANDing Result 11000000 10101000 00000001 00000000
Host B’s IP address 11000000 10101000 00000001 00010100
Host B’s subnet mask 11111111 11111111 11111111 00000000
ANDing Result 11000000 10101000 00000001 00000000
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General Guidelines for IP Addressing
All hosts on the same physical network should
have the same network ID.
Each host on a network segment must have a
unique host portion of the IP address.
A network ID never be 127.x.x.x .
A host ID cannot be all 1s.
A host ID cannot be all 0s.
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Limitations of Classful Addressing
No network class was designed to support
medium-sized organizations.
Allocation of IP address is not efficient.
It causes depletion of the network address space.
The size of the global Internet’s routing table is
increasing.
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Subnetting Solution
There are a situations that require you to segment the
network using a subnet mask that is not the default
subnet mask.
The host portion is now broken into a subnet portion and
host portion
Two-level Classful
Network Number Host Number
Three-level Subnet
Network Number Subnet Number Host Number
Extended Network Prefix
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Subnet Designing
Before design, the following questions must be
answered.
How many network segments does the network need
addresses for today and in the future?
How many hosts will be needed on the largest segment
of the network today and the future?
Three steps for subnet designing.
Determining the number of subnets.
Determining the number of hosts.
Establishing the available pools of IP addresses.
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Determining the Number of Subnets
Each individual network segment requires a
unique network number.
Net#1 Net#2
Net#3
Net#4
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Zero Subnetting
The subnetwork addresses of all zeros or all ones
are not allowed in many networking
implementations.
Zero subnetting is a feature that allows routers
supporting advanced routing protocols to use the
subnetwork addresses of all zeros and all ones.
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Determining the Number of Hosts
Number of hosts is calculated by the bits left from
the first step using the following formula.
2n – 2
The “n” is the number of bits left.
The number 2 is subtracted because a host
address cannot be all zeros or all ones.
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Establishing the Pools of IP Addresses
The final step is to identify the actual address
that can be assigned to hosts in the network
segments.
Two IP addresses cannot be used.
The first address, which all host IDs are zero, is the
network address.
The last address, which all host IDs are one, is the
broadcast address.
The available pool begins with the address
immediately following the network address and
ends with the address before the broadcast
address.
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Variable-Length Subnet Masking
VLSM enables each subnet to have its own unique
subnet mask.
If the subnet mask is not included in the routing
protocol, the VLSM can not be implemented.
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Classless Inter-Domain Routing
CIDR removes the concept of Class A, Class B,
Class C address.
Every address simply contains network and host
portions.
CIDR supports route aggregation that a single
route can represent the thousands of actual
routes.
All routers must advertise both the network
address and the subnet mask.
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