Transcript Chapter 2 IP Address

IP address
• Universally accepted addressing method is
required so that all hosts can communicate
with each other
• TCP/IP based network is assigned with
unique addresses known as IP addresses
IP address
• Network layer addresses (IP addresses) are
32 bits long.
• Presented as four octets in dotted decimal
format.
• IP address has two components: Network ID
and Host ID.
IP address format
IP address classes
H
H
H
H
H
H
• Different class addresses reserve different
amounts of bits for Network and Host portions
of the address
• Provide flexibility required to support different
size networks
IP address classes: Class A
IP address classes: Class A
• First bit of a Class A address is always 0.
• First 8 bits identify network part of the address.
• Possible network address from 1.0.0.0 to
127.0.0.0.
• Remaining three octets used for the host portion
of the address.
• Each class A network have up to 16,777,214
possible IP addresses.
IP address classes: Class B
IP address classes: Class B
• First 2 bits of Class B address is always 10.
• First two octets identify network part of the
address.
• Possible network address from 128.1.0.0 to
191.254.0.0.
• Remaining two octets used for host portion of
the address.
• Class B network have up to 65.534 possible IP
addresses.
IP address classes: Class C
IP address classes: Class C
• First 3 bits of a Class C address is always 110.
• First three octets identify network part of the
address.
• Possible network address from 192.0.1.0 to
223.255.254.0.
• Remaining last octet used for host portion of
the address.
• Class C network have up to 254 possible IP
addresses.
Binary and decimal conversion
Fast conversion
Bits on the IP address
• Network Bits :
– Identifies network ID
– Identifies class of the IP address
– All of bits are 0: not allowed
• Host Bits :
– Identifies host ID
– All of bits are 0: reserved for network address
– All of bits are 1: reserved for broadcast address
IP address classes: Summary
•
•
•
•
•
1.0.0.0 - 126.0.0.0 : Class A.
127.0.0.0 : Loopback network.
128.1.0.0 - 191.254.0.0 : Class B.
192.0.1.0 - 223.255.254.0 : Class C.
224.0.0.0 - 239.255.255.255: Class D,
multicast.
• >= 240.0.0.0 : Class E, reserved.
Network address
• provide a convenient way to refer to all of
the addresses on a particular network or
subnetwork.
• Two hosts with differing network address
require a device, typically a router, in order
to communicate.
• An IP address that ends with binary 0s in all
host bits is reserved for the network address.
Broadcast address
• Broadcast goes to every host with a
particular network ID number.
• IP address that ends with binary 1s in all host
bits is reserved for the directed broadcast
address.
• An IP address with binary 1s in all network
bits and host bits is reserved for the local
broadcast address.
Example: 172.16.20.200
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•
•
•
•
172.16.20.200 is Class B address
Network portion: 172.16
Host portion:
20.200
Network address: 172.16.0.0
Broadcast address: 172.16.255.255
Private addresses
• According to RFC-1918.
• Organizations make use of the private
Internet address space for hosts that require
IP connectivity within their enterprise
network, but do not require external
connections to the global Internet.
• Class A: 10.0.0.0.
• Class B: 172.16.0.0 - 172.31.0.0.
• Class C: 192.168.0.0 - 192.168.255.0.
Reserved addresses
•
The bits that define the host portion of an
IP address should not be all “1”. Any IP
address with the host portion consisting of
all “1” is interpreted as “all host”.
–
Example : 128.1.255.255 means all hosts on
network number 128.1
Reserved addresses
•
The bits that define the host portion of an
IP address should not be all “0”. Any IP
address with the host portion consisting of
all “0” is interpreted as network address.
–
Example : 128.1.0.0 means network number.
Reserved addresses
•
The bits used to define the network
portion of an IP address should not be all
“0”. A network portion address of all “0”
is interpreted as “this network”.
–
Example : 0.0.0.63 means Host 63 on this
network.
Reserved addresses
•
The Class A network number 127.x.x.x is
assigned as “Loop-back” function. This
means that a datagram sent by a higherlevel protocol to a Network 127 address
should loop back inside the host.
Review
• Classes of IP address and range of IP on each
class.
• Determine network portion and host portion in
a IP address.
• Understand about broadcast addresses.
• Understand about valid host address.
• Binary and Decimal conversion.
Introduction to Subnetworks
What Is a Subnet?
• Series of Networks within a Network
• Created by subdividing Host address field
and creating a Subnetwork Field
• All Hosts on a Subnetwork share a common
subnetwork address
Why Subnet a Network?
• Provides Greater Organization of Large
Networks (Class A 16 Million Hosts!)
• Allows Additional Networks (subnets)
without applying for additional IPs
• Gives local administrators more control
• Provides a Third Level of Hierarchy
• Reduces the Size of Broadcast Domains
How Do You Create Subnets?
• Bits are Borrowed from the Host Field
– This Creates a Subnet Field in the IP address
Class C Subnets
Network
S
Network
S
H
H
Network
H
H
Host
H
H
Two Bits Borrowed from the Host Field to form a
third layer of hierarchy - A Subnet Field
Two Bits must always remain so a maximum of 6
Bits may be borrowed from a Class C network
How many bits can be borrowed from a Class B
network? From a Class A network?
Class C Subnets
Network
S
Network
S
H
H
Network
H
H
Host
H
H
The number of Subnets Created is calculated using
the following formula:
# Subnets Created = 2# Borrowed Bits
Class C Subnets
S
S
H
H
H
H
H
H
Borrow 2 Bits = 22 = 4 Subnets
S
S
S
H
H
H
H
H
Borrow 3 Bits = 23 = 8 Subnets
S
S
S
S
H
H
H
H
Borrow 4 Bits = 24 = 16 Subnets
Class C Subnets
S
S
S
S
S
H
H
H
Borrow 5 Bits = 25 = 32 Subnets
S
S
S
S
S
S
H
H
Borrow 6 Bits = 26 = 64 Subnets
Borrow 7 Bits = Cannot
Two Host Bits Must Remain
How Many Subnets?
Borrow 2 Bits = 22 = 4 Subnets
• If you Borrow 2 Host Bits you do NOT get
4 Subnets. Why?
• Remember the Network Address and
Broadcast Address - Both of these addresses
are Reserved, they cannot be used!
How Many Hosts/Subnet?
Network
S
Network
S
H
H
Network
H
H
Host
H
H
The number of Hosts per subnet is calculated using
the following formula:
# Hosts/Subnet = 2# Host Bits Remaining
# Hosts = 26 = 64 hosts/subnet
How Many Hosts/Subnet?
6 Host Bits Remain = 26 = 64 Hosts
• If there are 6 Host Bits remaining you do
NOT get 64 Hosts/Subnet. Why?
• Each subnetwork has its own Subnetwork
Address and Broadcast Address - Both of
these addresses are Reserved and cannot be
used!
• Thus only 62 Hosts are available.
Formulas to Remember!
# Subnets Created = 2# Borrowed Bits
• Remember to subtract 2 for the Network
Address and Broadcast Address.
# Hosts/Subnet = 2# Host Bits Remaining
• Remember to subtract 2 for the Subnetwork
Address and Subnetwork Broadcast
Address.
Determining Network/Host ID
• Given 2 IP addresses 192.20.1.5.and
192.20.6.8. The subnet mask is
255.255.255.0. Determine the network
address and the host address, also decide
whether the message need to be send
through the router.
Determining Network/Host ID
192.20.1.5
=
255.255.255.0 =
Network ID =
Host ID
=
192.20.6.8
=
255.255.255.0 =
Network ID =
Host ID
=
11000000.00010100.00000001.00000101
11111111.11111111.11111111.00000000
11000000.00010100.00000001.00000000
=> 192.20.1.0
00000000.00000000.00000000.00000101
=> 0.0.0.5
11000000.00010100.00000110.00001000
11111111.11111111.11111111.00000000
11000000.00010100.00000110.00000000
=> 192.20.6.0
00000000.00000000.00000000.00001000
=> 0.0.0.8
Determining Network/Host ID
• Given 2 IP addresses 192.20.1.5 and
192.20.6.8. The subnet mask is 255.255.0.0.
Determine the network address and the host
address, also decide whether the message
need to be send through the router.
Determining Network/Host ID
192.20.1.5
255.255.0.0
Network ID
=
=
=
Host ID
=
192.20.6.8
255.255.0.0
Network ID
=
=
=
Host ID
=
11000000.00010100.00000001.00000101
11111111.11111111.00000000.00000000
11000000.00010100.00000000.0000
=> 192.20.0.0
00000000.00000000.00000001.00000101
=> 0.0.1.5
11000000.00010100.00000110.00001000
11111111.11111111.00000000.00000000
11000000.00010100.00000000.00000000
=> 192.20.0.0
00000000.00000000.00000110.00001000
=> 0.0.6.8
Determining Network/Host ID
• Suppose a Class B IP address is 191.20.0.0
and the subnet mask is 255.255.224.0. Find
the number of subnet available and state the
subnet addresses. How many hosts can
each subnet have ?
Determining Network/Host ID
191.20.x.x
= 10111111.00010100.xxxxxxxx.xxxxxxxx
255.255.224.0 = 11111111.11111111.11100000.00000000
Network ID = 10111111.00010100.xxx00000.00000000
=> 191.20.x.0
As extra 3 bits is added into the subnet mask, we have increased the
bits available for the network ID. Now, we can have 6 [(2^3) –
2 ] different Network ID.
Determining Network/Host ID
10111111.00010100.00100000.00000000
10111111.00010100.01000000.00000000
10111111.00010100.01100000.00000000
10111111.00010100.10000000.00000000
10111111.00010100.10100000.00000000
10111111.00010100.11000000.00000000
=>
=>
=>
=>
=>
=>
Each subnet can have [2^13 –2] = 8190 hosts.
191.20.32.0
191.20.64.0
191.20.96.0
191.20.128.0
191.20.160.0
191.20.192.0