Chapter 6 (Cont.) IP ADDRESSING Subnetting CIDR · IP ADDRESSING – Subnetting CIDR 1 . IP...
Transcript of Chapter 6 (Cont.) IP ADDRESSING Subnetting CIDR · IP ADDRESSING – Subnetting CIDR 1 . IP...
Chapter 6 (Cont.)
IP ADDRESSING – Subnetting
CIDR
1
IP Addresses
An IP address is an address used to uniquely identify a
device on an IP network.
• It designates the specific location of a device on the network.
• IP addressing was designed to allow hosts on one network to
communicate with a host on a different network regardless of
the type of LANs the hosts are participating in.
The address is made up of 32 binary bits which can be
divisible into a network portion and host portion with the help
of a subnet mask.
32 binary bits are broken into four octets (1 octet = 8 bits)
Dotted decimal format (for example, 172.16.81.100)
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Network Addressing
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Subdividing an IP address into a network and node address
is determined by the class designation of one’s network. This
figure summarizes the three classes of networks
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IP Address Classes
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IP Address Classes
• Class A: The first octet is the network portion. Octets 2, 3,
and 4 are for subnets/hosts
• Class B: The first two octets are the network portion. Octets 3
and 4 are for subnets/hosts
• Class C: The first three octets are the network portion. Octet 4
is for subnets/hosts
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Private Address Range
Address Class Reserved Address Space
Class A 10.0.0.0 - 10.255.255.255
Class B 172.16.0.0 - 172.31.255.255
Class C 192.168.0.0 - 192.168.255.255
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IP Terminology
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BIT: A bit is one digit, either a 1 or a 0.
BYTE: A byte is 7 or 8 bits, depending on whether parity is used. For
the rest of this chapter, always assume a byte is 8 bits.
OCTET: An octet, made up of 8 bits, is just an ordinary 8-bit binary
number. In this chapter, the terms byte and octet are completely
interchangeable.
Network address: This is the designation used in routing to send
packets to a remote network—for example, 10.0.0.0, 172.16.0.0, and
192.168.10.0.
Broadcast address: The address used by applications and hosts to
send information to all nodes on a network is called the broadcast
address. 7
Reserved Addressing
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Address Function
Network address of all 0s Interpreted to mean “this network or segment.”
Network address of all 1s Interpreted to mean “all networks.”
Network 127.0.0.1 Reserved for loopback tests.
Node address of all 0s Interpreted to mean “network address” or
any host on specified network.
Node address of all 1s Interpreted to mean “all nodes” on the
specified network
Entire IP address set to all 0s Used by Cisco routers to designate the
default route. Could also mean “any network.”
Entire IP address set to all 1s (same as Broadcast to all nodes on the
current network; 255.255.255.255)
sometimes called an “all 1s broadcast” or limited broadcast
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Private Addressing
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Address Class Reserved Address Space
Class A 10.0.0.0 through 10.255.255.255
Class B 172.16.0.0 through 172.31.255.255
Class C 192.168.0.0 through 192.168.255.255
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Network Masks
• Distinguishes which portion of the address identifies
the network and which portion of the address
identifies the node.
• Default masks:
Class A: 255.0.0.0
Class B: 255.255.0.0
Class C: 255.255.255.0
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Subnetting
Subnetting is a technique used to break down (or partition)
networks into subnets. The subnets are created through the
use of subnet masks.
Creates multiple logical networks that exist within a single
Class A, B, or C network.
If you do not subnet, you will only be able to use one network
from your Class A, B, or C network, which is unrealistic
Each data link on a network must have a unique network ID,
with every node on that link being a member of the same
network
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The subnets are created by borrowing bits from the host portion of the IP address as shown.
The network portion of the IP address and the new subnet bits are used to define the new subnet. Routers use this information to properly forward data packets to the proper subnet.
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The Class C network, shown is partitioned into four subnets. It takes 2 bits to provide four possible subnets therefore 2-bits are borrowed from the host bits.
This means the process of creating the four subnets reduces the number of bits available for host IP addresses.
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Benefits of Subnetting
1) Reduced network traffic
2) Optimized network performance
3) Simplified management
4) Facilitated spanning of large geographical distances
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How to create subnets
Determine the number of required network IDs:
One for each subnet
One for each wide area network connection
Determine the number of required host IDs per subnet:
One for each TCP/IP host
One for each router interface
Based on the above requirements, create the following:
One subnet mask for your entire network
A unique subnet ID for each physical segment
A range of host IDs for each subnet
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No Subnetting
• All hosts think that the other hosts are on the same network
128.143.0.0/16
128.143.137.32/16subnetmask: 255.255.0.0
128.143.71.21/16
subnetmask: 255.255.0.0
128.143.137.144/16
subnetmask: 255.255.0.0
128.143.71.201/16subnetmask: 255.255.0.0
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128.143.0.0/16
128.143.137.32/24
subnetmask: 255.255.255.0
128.143.71.21/24
subnetmask: 255.255.255.0
128.143.137.144/24
subnetmask: 255.255.255.0
128.143.71.201/24
subnetmask: 255.255.255.0
128.143.137.0/24
Subnet
128.143.71.0/24
Subnet
With Subnetting
• Hosts with same extended network prefix belong to the same
network
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• Different subnetmasks lead to different views of the scope of
the network
128.143.0.0/16
128.143.137.32/26
subnetmask: 255.255.255.192
128.143.71.21/24
subnetmask: 255.255.255.0
128.143.137.144/26
subnetmask: 255.255.255.192
128.143.71.201/16
subnetmask: 255.255.0.0
128.143.71.0/24
Subnet128.143.137.128/26
Subnet
128.143.137.0/26
Subnet
With Subnetting
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Subnetting
• Scenario: Organization has
a large network prefix and
wants to create smaller
networks.
• Subnetting: Use a portion
of the host name to identify
a smaller network
(“subnetwork”, “subnet”).
• Each subnet becomes a separate
network
UofT Network
Faculty of A&S
Library
Faculty of
Engineering
128.100.0.0/16
128.100.11.0/24 128.100.58.0/24
128.100.136.0/24
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Subnetting Basics
• Benefits of subnetting include:
– Reduced network traffic
– Optimized network performance
– Simplified management
– Facilitated spanning of large geographical distances.
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Advantages of Subnetting
• With subnetting, IP addresses use a 3-layer hierarchy:
» Network
» Subnet
» Host
• Reduces router complexity. Since external routers do not
need to know about subnetting, the complexity of routing
tables at external routers is reduced.
• Flexibility: Length of the subnet mask need not be identical on
all subnetworks.
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How To Create Subnets
Take bits from the host portion of the IP address and
reserve the to divine the subnet address.
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Understanding the Powers of 2
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Subnet Masks
• Used to define which part of the host address will be used
as the subnet address.
• A 32-bit value that allows the recipient of IP packets to
distinguish the network ID portion of the IP address from
the host ID portion.
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Subnetting
and
Supernetting
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• IP address consists of a network prefix and a host number
• Prefix notation: 128.100.__.__/16
• Notation with netmask: 128.100.__.__
255.255.0.0
Network Prefix and Host number
255 0 0
128.100
network prefix host number
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
255
netmask
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• IP address consists of a network prefix and a host number
• Prefix notation: 128.100.__.__/__
• Notation with netmask: 128.100.__.__
255.255.__.__
Actual Network Prefix
255 0 0
128.100
network prefix host number
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
255
netmask
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Basic Idea of Subnetting
• Split the host number portion of an IP address into a subnet number and a (smaller) host number.
• Result is a 3-layer hierarchy
• Then: • Subnets can be freely assigned within the organization
• Internally, subnets are treated as separate networks
• Subnet structure is not visible outside the organization
network prefix host number
subnet number network prefix host number
extended network prefix
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• Start of the host number is indicated by prefix or netmask notation
• The netmask of the extended network prefix is called subnetmask (and
the nework is called subnet)
Subnetmask
128.100 11.60
network prefix host number
128.100 60
network prefix host number subnet
number
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extended network prefix
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0
subnetmask
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