Subnet Masking
IPV4 Address & Subnet Masks
IP addresses:
Example IP Addresses:
135.68.2.0 (Internet)
135.68.2.1 (Marketing)
135.68.1.0
135.68.3.0
135.68.2.2
135.68.3.1
135.68.3.2 (Engineering)
Understanding IPv4 Addressing
myIP address: 72.35.208.20
IPv4 Address:
Binary Representation:
01001000.00100011.11010000.00010100
Binary structure: 8 bits per octet resulting in a total of 32 bits (8 * 4 bits).
Address Components:
Street
City
State
Zipcode
Conversion from Binary to Decimal
For Each Octet
First octet: [See YouTube for details]
Second octet: [Conversion Methodology]
Third octet: [Conversion Methodology]
Fourth octet: [Conversion Methodology]
Converting Decimal IP Addresses to Binary
Example IP Address: 165.58.199.43
Conversion Steps:
128 ≤ 165 → 128 64 32 16 8 4 2 1
Calculation Steps for 165:
165 - 128 = 37
Calculation Steps for next values:
37 - 32 = 5
5 - 4 = 1
IPv4 Address Structure
Definition: An IP address is a 32-bit long value represented in binary as a string of zeros and ones (e.g., 11000000.10101000.00000100.00000010).
Octets:
Consists of 4 octets (each octet being 8-bits).
Each octet is represented in binary as 00000000 to 11111111.
Decimal Representation:
IP addresses in decimal notation are 4 decimal numbers separated by dots (e.g., 192.168.4.2).
Subnet Masks
Subnet Mask Example:
In decimal: 255.255.255.0
Binary format: 11111111.11111111.11111111.00000000
CIDR notation: /24
Subnetting:
Represents the practice of dividing a network into two or more networks.
Understanding Subnetting
Subnetwork:
Definition: A logical subdivision of an IP network.
Addressing: Computers within a subnet share the same most-significant bit-group in their IP addresses, creating a division into a network number and a host identifier.
CIDR Example:
Notation: 198.51.100.0/24
At this address, 24 bits are allocated for the network prefix, while 8 bits are for host addressing.
Subnetting Process
Before Subnetting:
Network identifier, IP address, host identifier.
After Subnetting:
Network identifier, subnet identifier, host identifier.
Subnet Masks Variations
Subnet Mask Examples:
/18 → 255.0.0.0 (binary: 11111111.00000000.00000000.00000000)
/16 → 255.255.0.0 (binary: 11111111.11111111.00000000.00000000)
/15 → 248.0.0.0 (binary: 11111000.00000000.00000000.00000000)
Communication Process in Networking
Local Communication
Devices Involved:
Switch: Layer 2 device used for local communication
MAC Address: Used for local communication
IP Address: Used for remote communication
Default Gateway: Layer 3 device used for remote communications.
Remote Communication
Step 1: Computer A uses ARP protocol to obtain the MAC address of the Default Gateway.
Step 2: Default Gateway replies with its MAC address.
Step 3: Computer A sends IP packets to the Default Gateway for delivery.
Example of Subnetting Tasks
Example Subnet Task: Set up 3 separate subnets for the department based on a provided network ID of 125.23.200.64/26
Network IDs:
125.23.200.64/28 ranges from 125.23.200.65-125.23.200.78 (Broadcast: 125.23.200.79)
125.23.200.80/28 ranges from 125.23.200.81-125.23.200.94 (Broadcast: 125.23.200.95)
125.23.200.96/28 ranges from 125.23.200.97-125.23.200.110 (Broadcast: 125.23.200.111)
Network Classifications
Each class divined by the first octet ranges from IP 0-255:
Class A: 0-127
Class B: 128-191
Class C: 192-223
Class D (Multicast): 224-239
Class E (Experimental): 240-255
Subnet Masks for each class
Across classes, subnet masks dictate how many usable hosts per network can exist.
Additional Addresses
Broadcast Address: An address used to communicate to all systems in a subnet rather than a single host.
Host Calculation
Formula for calculating usable hosts per network:
(where = number of zeros).
Formula for calculating number of networks:
(where = number of ones).