IP Addressing
Objectives:
 Internet Architecture
IPv4 Addressing
IP address Classes
Subnets and subnet mask
Subnets design with IP addressing
IPv6
Internet Architecture
Taibah University
• Two computers, anywhere in
the world, following certain
hardware, software, protocol
specifications, can
communicate, reliably even
when not directly connected.
• LANs are no longer scalable
beyond a certain number of
stations or geographic
separation.
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Internet Addresses
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IP Address as a 32-Bit Binary Number
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Decimal Equivalents of 8-Bit Patterns
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Binary and Decimal Conversion
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IP Address Classes
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IP Address Classes
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IP Addresses as Decimal Numbers
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Hosts for Classes of
IP Addresses
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Class A (24 bits for hosts) 224 - 2* = 16,777,214 maximum hosts
Class B (16 bits for hosts) 216 - 2* = 65,534 maximum hosts
Class C (8 bits for hosts) 28 - 2* = 254 maximum hosts
*
Subtracting the network and broadcast reserved address
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IPv4 Address Classes
Taibah University
Class D Addresses
• A Class D address begins with binary 1110 in the first octet.
• First octet range 224 to 239.
• Class D address can be used to represent a group of hosts called a
host group, or multicast group.
Class E Addresses
• First octet of an IP address begins with 1111
• First octet range 240 to 255.
• Class E addresses are reserved for experimental purposes and should
not be used for addressing hosts or multicast groups.
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IP Addresses as Decimal Numbers
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Network IDs and Broadcast Addresses
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An IP address such as 176.10.0.0 that has all binary 0s in
the host bit positions is reserved for the network address.
An IP address such as 176.10.255.255 that has all binary 1s
in the host bit positions is reserved for the broadcast
address.
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Private Addresses
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Reserved Address Space
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• Network ID
• Broadcast address
• Hosts for classes of IP addresses
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Basics of Subnetting
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• Classical IP addressing
• Subnetworks
• Subnet mask
• Boolean operations: AND, OR, and NOT
• Performing the AND function
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Subnetworks
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To create a subnet address, a network administrator
borrows bits from the original host portion and
designates them as the subnet field.
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Subnetworks
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Subnet Mask
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• Determines which part of an IP address is the network field and which
part is the host field
• Follow these steps to determine the subnet mask:
– 1. Express the subnetwork IP address in binary form.
– 2. Replace the network and subnet portion of the address with all
1s.
– 3. Replace the host portion of the address with all 0s.
– 4. Convert the binary expression back to dotted-decimal notation.
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Subnet Mask
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Subnet mask in decimal = 255.255.240.0
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Boolean Operations: AND, OR, and NOT
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• AND is like multiplication.
• OR is like addition.
• NOT changes 1 to 0, and 0 to 1.
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Performing the AND Function
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Range of Bits Needed to Create Subnets
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Subnet Addresses
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Creating a Subnet
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•
•
•
•
•
•
•
Determining subnet mask size
Computing subnet mask and IP address
Computing hosts per subnetwork
Boolean AND operation
IP configuration on a network diagram
Host and subnet schemes
Private addresses
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Determining Subnet Mask Size
Taibah University
Class B address with 8 bits borrowed for the subnet
130.5.2.144 (8 bits borrowed for subnetting) routes to subnet
130.5.2.0 rather than just to network 130.5.0.0.
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Determining Subnet Mask Size
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Class C address 197.15.22.131 with a subnet
mask of 255.255.255.224 (3 bits borrowed)
11000101
00001111
Network Field
00010110
100
00011
SN
Host Field
The address 197.15.22.131 would be on the
subnet 197.15.22.128.
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Subnetting Example with AND Operation
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IP Configuration on a Network Diagram
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The router connects subnetworks and networks.
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Subnet Example
Taibah University
Given the Class B address 190.52.0.0
Class B
Using /24
subnet...
Network Network
Network Network
Host
Subnet
Host
Host
Internet routers still “see” this net as 190.52.0.0
190.52.1.2
190.52.2.2
190.52.3.2
But internal routers think all
these addresses are on different
networks, called subnetworks
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Subnet Example
Taibah University
Network Network
Subnet
Host
Using the 3rd octet, 190.52.0.0 was divided into:
190.52.1.0
190.52.5.0
190.52.9.0
190.52.13.0
190.52.17.0
190.52.2.0
190.52.6.0
190.52.10.0
190.52.14.0
190.52.18.0
190.52.3.0
190.52.7.0
190.52.11.0
190.52.15.0
190.52.19.0
190.52.4.0
190.52.8.0
190.52.12.0
190.52.16.0
and so on ...
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Subnet Example
Taibah University
Network address 190.52.0.0 with /16 network mask
Using Subnets: subnet mask 255.255.255.0 or /24
Network Network
Subnet
Host
190
190
52
52
0
1
Host
Host
190
190
190
190
52
52
52
52
2
3
Etc.
254
Host
Host
Host
Host
190
52
255
Host
Subnets
255
Subnets
28 - 1
Cannot use last
subnet as it
contains broadcast
address
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Subnet Example
Taibah University
Subnet 0 (all 0’s subnet) issue: The address of the subnet,
190.52.0.0/24 is the same address as the major network,
190.52.0.0/16.
Network Network Subnet
Host
190
190
52
52
0
1
Host
Host
190
190
52
52
Etc.
254
Host
Host
Subnets
255
Subnets
28 - 1
190
52
255
Host
Last subnet (all 1’s subnet) issue: The broadcast address for
the subnet, 190.52.255.255 is the same as the broadcast
address as the major network, 190.52.255.255.
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Host Subnet Schemes
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The number of lost IP addresses with a Class C network
depends on the number of bits borrowed for subnetting.
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IP addressing crisis
Taibah University
•
•
Address Depletion
Internet Routing Table Explosion
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IPv4 Addressing
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Subnet Mask
• One solution to the IP address shortage was thought to be the
subnet mask.
• Formalized in 1985 (RFC 950), the subnet mask breaks a single
class A, B or C network in to smaller pieces.
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Short Term Solutions: IPv4 Enhancements
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CIDR (Classless Inter-Domain Routing) – RFCs 1517,
1518, 1519, 1520
VLSM (Variable Length Subnet Mask) – RFC 1009
Private Addressing - RFC 1918
NAT/PAT (Network Address Translation / Port Address
Translation) – RFC
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IPv4 versus IPv6
Taibah University
• IP version 6 (IPv6) has been defined and developed.
• IPv6 uses 128 bits rather than the 32 bits currently used in IPv4.
• IPv6 uses hexadecimal numbers to represent the 128 bits.
IPv4
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Long Term Solution: IPv6 (coming)
Taibah University
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•
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•
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IPv6, or IPng (IP – the Next Generation) uses a 128-bit address
space, yielding
340,282,366,920,938,463,463,374,607,431,768,211,456
possible addresses.
IPv6 has been slow to arrive
IPv4 revitalized by new features, making IPv6 a luxury, and not
a desperately needed fix
IPv6 requires new software; IT staffs must be retrained
IPv6 will most likely coexist with IPv4 for years to come.
Some experts believe IPv4 will remain for more than 10 years.
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