IP ADDRESSING

ANALYZING CLASSFUL IPV4 NETWORKS

CLASSFUL NETWORK CONCEPTS This chapter examines how to begin with a single IP address and then determine the following facts:

•  Class (A, B, or C) •  Default mask •  Number of network octets/bits •  Number of host octets/bits •  Number of host addresses in the network •  Network ID •  Network broadcast address •  First and last usable address in the network

Class (A, B, or C)

CLASS (A, B, OR C) CONTINUED

CLASS (A, B, OR C) NUMBERS

DEFAULT MASK

Number of network octets/bits Number of host octets/bits

DERIVING THE NETWORK ID AND RELATED NUMBERS Each classful network has four key numbers that describe the network.

•  Network number •  First (numerically lowest) usable address •  Last (numerically highest) usable address •  Network broadcast address

EXAMPLE OF DERIVING THE NETWORK ID AND OTHER VALUES FROM 10.17.18.21

PRACTICE WITH CLASSFUL NETWORKS

INTRODUCTION TO SUBNETTING

SUBNET PLANNING, DESIGN, AND IMPLEMENTATION TASKS

ANALYZE SUBNETTING AND ADDRESSING NEEDS Which hosts should be grouped together into a subnet? How many subnets does this network require? How many host IP addresses does each subnet require?

Will we use a single subnet size for simplicity, or not?

SUBNET SIZE CONCEPTS

MAKE DESIGN CHOICES

PRIVATE IP NETWORK ADDRESSES

UNSUBNETTED CLASSFULL NETWORKS

CONCEPT OF BORROWING FROM HOST TO INCREASE NUMBER OF NETWORKS

SUBNET Subnet number: Also called the subnet ID or subnet address, this number identifies the subnet. It is the numerically smallest number in the subnet. It cannot be used as an IP address by a host. Subnet broadcast: Also called the subnet broadcast address or directed broadcast address, this is the last (numerically highest) number in the subnet. It also cannot be used as an IP address by a host. IP addresses: All the numbers between the subnet ID and the subnet broadcast address can be used as a host IP address.

PLAN THE IMPLEMENTATION

EXAMPLE OF SUBNETS ASSIGNED TO DIFFERENT LOCATIONS

THREE MASK FORMATS 32-bit binary numbers

•  11111111 00000000 00000000 00000000!•  11111111 11111111 11111111 00000000!

Dotted Decimal Notation (DDN)

•  255.0.0.0!•  255.255.255.0!

Prefix (also called CIDR) •  /8!•  /24!

CONVERTING BETWEEN BINARY AND PREFIX MASKS

CONVERTING BETWEEN BINARY AND DDN MASKS

EXAMPLE CONVERSIONS

CONVERSION FROM PREFIX TO DECIMAL: FULL BINARY VERSUS SHORTHAND

CONVERSION FROM DECIMAL TO PREFIX: FULL BINARY VERSUS SHORTHAND

PRACTICE CONVERTING SUBNET MASKS