IPv4 and Subnetting

CIDR notation Address class is no longer uniquely identifiable from the address  We must find a way of telling routers the size of the network part of the address  Done by including a number along with the network address  E.g / 17 In the above example, the first 17 bits of the address are the network part You can search for more example CIDR address blocks at

CIDR notation The CIDR notation will tell you how many IP addresses are available in that subnet.

How does a company allocate a large pool of addresses? Ex. UNCW has / 16 which gives them a possible 65,536 IP addresses (2 (32-16) ) Possible approach to assigning IP addresses: As soon as a computer comes online, you can assign them the next IP address available. Desktop in CIS Laptop in Union Workstation in Library

How does a company allocate a large pool of addresses? Alternative Method: Each college or building allocated a contiguous set of IP addresses Desktop in CIS Laptop in Union Workstation in Library CIS Fisher Union Library

Subnetting and network structure Each Ethernet is given a unique subnetwork ID  Enables broadcasting within the Ethernet  Each computer on the Ethernet must be part of this network Subnetting enables the partition of a large address pool into multiple smaller blocks

Subnets and IP Addresses What does UNCW’s IP Addresses look like?

3-part interpretation of IP addresses 8

Subnets - How do you decide who gets what address? Group of computers on the same LAN with IP numbers using the same prefix Assigned addresses  For example: Subnet x – Computers in CIS labs (x is between 0 & 255) Subnet x & x – Computers in CIS Offices (x is between 0 & 255) Subnet x – Computers in Cameron Does anyone see a problem with the subnets above?

Subnet: Example CIS X X Cameron X Psych X Library X R R R R R Address: Address: Address: Address: Campus Backbone Address: X

Basic Subnetting How do we create 2 subnets?

Basic Subnetting How do we create 3 subnets?

Basic Subnetting How do we create 4 subnets?

Subnetting example Consider an organization with a /16 network address block ( / 16)  Most medium-large organizations fall in this category  Also, most State Universities  Say, after analysis, the organization settles on 5-bit subnet IDs

Example with 5-bit subnet IDs Subnet IDCampus unitSubnet IDCampus unitSubnet IDCampus unit (1)College (2)College (3)College (4)College (5)College (6)College (7)College (8)College (9)College (10)College (11) (12) (13)Dorm (14)Dorm (15) (16) (17)Branch campus (18)Branch campus (19) (20)Administration10101 (21)Campus IT (22) (23) (24) (25) (26) (27) (28) (29) (30)

Network ID + subnet ID for colleges in example Campus unitSubnet IDFirst 2 parts of IP addresses by college College _ _ _. _ _ _ _ _ _ _ _ College _ _ _. _ _ _ _ _ _ _ _ College _ _ _. _ _ _ _ _ _ _ _ College _ _ _. _ _ _ _ _ _ _ _ College _ _ _. _ _ _ _ _ _ _ _ College _ _ _. _ _ _ _ _ _ _ _ College _ _ _. _ _ _ _ _ _ _ _ College _ _ _. _ _ _ _ _ _ _ _ College _ _ _. _ _ _ _ _ _ _ _ College _ _ _. _ _ _ _ _ _ _ _

Complete subnet addresses for colleges in example Campus unitSubnet address (binary)Subnet address (decimal) College / 21 College / 21 College / 21 College / 21 College / 21 College / 21 College / 21 College / 21 College / 21 College / 21

Subnet Masks Used to make it easier to separate the subnet part of the address from the host part. Example  Subnet: x  Subnet mask: or in binary Example  Subnets: ,  Subnet mask or, in binary:

Subnet mask operation What does a subnet mask do?  The 0’s in the subnet mask block (mask) the corresponding bits in any destination address  The 1’s in the subnet mask allow the corresponding bits to be seen  The Result is the subnet address

How a network is setup for IP addresses Determine the Total Number of Hosts

How a network is setup for IP addresses Determine the Number and Size of the Networks

How a network is setup for IP addresses Allocating Addresses

How a network is setup for IP addresses Allocating Addresses

How a network is setup for IP addresses Within the address range of each IPv4 network, we have three types of addresses: Network address - The address by which we refer to the network Broadcast address - A special address used to send data to all hosts in the network Host addresses - The addresses assigned to the end devices in the network

Case study – networks in the retail sector Both Wal-Mart and K-Mart started in 1962 K-Mart grew rapidly at first  250 stores in 1967, compared to 18 Wal-Marts  Each K-Mart store had 6 times the revenue of a Wal-Mart store 2002  K-Mart filed for bankruptcy  For the first time, Wal-Mart was the largest company in America by revenue

Among other factors Wal-Mart relied on IT  First computer network using phone lines in 1977 To improve inventory refills  Satellite network in 1987 Cut credit card processing time by half  EDI, RetailLink K-Mart relied on managerial expertise  Used spreadsheets to track supply and demand