CS-414 Chap 4 ( IP Address - Subnet Mask)

8/8/2019 CS-414 Chap 4 ( IP Address - Subnet Mask)

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Objectives:

Chapter 4: IP Addressing

Inter net ArchitectureIPv4 Addressing

IP address Classes

Subnets and subnet mask

Subnets design with IP addressingIPv6



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Inter net Architecture

Two computers, anywhere in

the world, f ollowing certain

hardware, software, pr otocol

specifications, can

communicate, reliably evenwhen not directly connected.

L ANs are no longer scalable

beyond a certain number of

stations or geographicseparation.



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IP Address as a 32-Bit Binary Number

Inter net Addresses



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Decimal Equivalents of 8-Bit Patter ns



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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

Class A (24 bits f or hosts) 224 - 2* = 16,777,214 maximum hosts

Class B (16 bits f or hosts) 216 - 2* = 65,534 maximum hosts

Class C (8 bits f or hosts) 28 - 2* = 254 maximum hosts

* Subtracting the network and broadcast reserved address



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IPv4 Address Classes

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 gr oup of hosts called ahost gr oup, or multicast gr oup.

Class E Addresses

First octet of an IP address begins with 1111

First octet range 240 to 255.

Class E addresses are reserved f or experimental purposes and shouldnot be used f or addressing hosts or multicast gr oups.



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IP Addresses as Decimal Numbers



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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.

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.

Network IDs and Broadcast Addresses



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Private Addresses



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Reserved Address Space

Network ID

Br oadcast address

Hosts f or classes of IP addresses



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Basics of Subnetting

Classical IP addressing

Subnetworks

Subnet mask

Boolean operations: AND, OR, and NOT Perf or ming the AND function



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Subnetworks

To create a subnet address, a network administrator

borr ows bits fr om the original host portion and

designates them as the subnet field.



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Subnetworks



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Subnet Mask

Deter mineswhich part of an IP address is the network field and which

part is the host field

Follow these steps to deter mine the subnet mask:

± 1. Express the subnetwork IP address in binary f or m. ± 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 in decimal = 255.255.240.0

Subnet Mask



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AND is like multiplication.

OR is like addition.

NOT changes 1 to 0, and 0 to 1.

Boolean Operations: AND, OR, and NOT



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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

Deter mining 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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Class B address with 8 bits borr owed f or the subnet

130.5.2.144 (8 bits borr owed f or subnetting) r outes to subnet

130.5.2.0 rather than just to network 130.5.0.0.

Determining Subnet Mask Size



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The address 197.15.22.131 would be on the

subnet 197.15.22.128.

11000101 00001111 00010110 100 00011

Network Field SN Host Field

Class C address 197.15.22.131 with a subnet

mask of 255.255.255.224 (3 bits borr owed)

Determining Subnet Mask Size



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Subnetting Example with AND Operation



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The r outer connects subnetworks and networks.

IP Configuration on a Network Diagram



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Using /24subnet...

190.52.1.2

190.52.2.2

190.52.3.2

Network Network Subnet Host

But internal routers think all

these addresses are on different

networks, called subnetworks

Internet routers still ³see´ this net as 190.52.0.0

Class B Network Network Host Host

Given the Class B address 190.52.0.0

Subnet Example



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Using the 3rd octet, 190.52.0.0 was divided into:

190.52.1.0 190.52.2.0 190.52.3.0 190.52.4.0

190.52.5.0 190.52.6.0 190.52.7.0 190.52.8.0

190.52.9.0 190.52.10.0 190.52.11.0 190.52.12.0

190.52.13.0 190.52.14.0 190.52.15.0 190.52.16.0

190.52.17.0 190.52.18.0 190.52.19.0 and so on ...


Subnet Example



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Subnet Example


Network address 190.52.0.0 with /16 network mask

190 52 0 Host

190 52 1 Host

190 52 2 Host

Using Subnets: subnet mask 255.255.255.0 or /24

190 52 3 Host

190 52 Etc. Host

190 52 254 Host

190 52 255 Host

255

Subnets

28 - 1

Cannot use last

subnet as it

contains broadcast

address

Subnets



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Subnet Example


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.

190 52 0 Host

190 52 1 Host

190 52 Etc. Host

190 52 254 Host

190 52 255 Host

255

Subnets

28 - 1

Subnets

Last subnet (all 1¶s subnet) issue: The br oadcast address f or the subnet, 190.52.255.255 is the same as the br oadcast

address as the major network, 190.52.255.255.



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The number of lost IP addresses with a Class C network

depends on the number of bits borrowed for subnetting.

Host Subnet Schemes



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IP addressing crisis

Address Depletion

Internet Routing Table Explosion



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IPv4 Addressing

Subnet Mask

One solution to the IP address shortage was thought to be the

subnet mask.

For malized 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

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

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)

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 f or years to come.

Some experts believe IPv4 will remain f or more than 10 years.

Documents

CS-414 Chap 4 ( IP Address - Subnet Mask)