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Subnet Calculator

Compute network parameters, subnet boundaries, and host ranges for IPv4 & IPv6
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CIDR Planner

Split a network into N equal subnets — IPv4 only
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Worksheet Generator

Generate printable subnetting practice worksheets with optional answer keys
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IP Addressing

IP Addressing Basics

Fundamental concepts of IPv4 and IPv6 addressing

IP (Internet Protocol) addresses are numerical labels assigned to devices connected to a network that uses the Internet Protocol for communication.

IPv4 vs IPv6

FeatureIPv4IPv6
Address Size32 bits128 bits
Address Format192.168.1.12001:0db8:85a3::8a2e:0370:7334
Available Addresses~4.3 billion~3.4×10³⁸
Header Size20–60 bytes40 bytes fixed

Network Components

Internet
ISP Router
Firewall
Security Gateway
Core Switch
Distribution Layer
End Devices
PCs, Servers

Key Concepts

  • Network Address: Identifies the network itself
  • Broadcast Address: Sends to all hosts on network
  • Subnet Mask: Distinguishes network and host portions
  • Gateway: Exit point from the network
IP Addressing

IP Address Classes

Traditional classful network architecture

IPv4 addresses are divided into classes to accommodate networks of different sizes.

Class A
1.0.0.0 – 126.x.x.x
Large Networks
Class B
128.0.0.0 – 191.x.x.x
Medium Networks
Class C
192.0.0.0 – 223.x.x.x
Small Networks

Class Characteristics

ClassFirst OctetNetwork BitsHost BitsNetworksHosts/Net
A1–12682412616,777,214
B128–191161616,38465,534
C192–2232482,097,152254
IP Addressing

CIDR Notation

Classless Inter-Domain Routing — modern flexible addressing

CIDR replaces classful network architecture with flexible prefix lengths, enabling efficient IP allocation and route aggregation.

CIDR vs Classful

Classful
Fixed Classes
A, B, C, D, E
CIDR
Flexible Mask
/8 to /32

Benefits

  • Efficient Allocation: No wasted IP space
  • Flexible Subnetting: Any prefix length
  • Route Aggregation: Reduces routing table size
  • Modern Standard: Used in all modern networks

Common CIDR Examples

CIDRSubnet MaskUsable HostsUse Case
/24255.255.255.0254Small Business
/26255.255.255.19262Department
/30255.255.255.2522Point-to-Point
Network Security

Firewalls

Network security systems for traffic monitoring and access control

Firewalls monitor and control network traffic based on predetermined security rules, forming the first line of defence.

Firewall Types

Packet Filtering
Stateless
Basic filtering
Stateful
Connection Tracking
Modern standard
Next-Generation
Application-Aware
Deep inspection

Deployment

Network Layout: Internet → Firewall → Internal Network

Common Use Cases

  • Enterprise Networks: Protect internal resources from external threats
  • DMZ Setup: Isolate public-facing servers
  • Remote Access: Secure VPN connections
  • Compliance: Meet regulatory requirements (PCI-DSS, ISO 27001)
Network Security

IDS & IPS

Intrusion Detection and Prevention Systems

IDS and IPS monitor network traffic for suspicious activity and policy violations, providing active threat response capabilities.

IDS vs IPS Comparison

FeatureIDSIPS
Primary FunctionDetection & AlertingDetection & Prevention
Network PositionOut-of-bandIn-line
ResponsePassiveActive
Impact on TrafficNoneCan block/drop packets

Deployment Architecture

Internet
External Network
Firewall
Traffic Filter
IPS
Active Protection
Internal Network
Protected Assets

Detection Methods

  • Signature-based: Known attack patterns
  • Anomaly-based: Behavioural analysis
  • Policy-based: Rule violations
  • Heuristic: Machine learning patterns
Network Security

VPN Technology

Virtual Private Networks — secure encrypted tunnelling

VPNs create secure, encrypted connections over public networks, enabling remote access and site-to-site connectivity.

VPN Types

Site-to-Site
Office Connections
LAN to LAN
Remote Access
Individual Users
Client to Network
SSL VPN
Web-based Access
No client software

VPN Protocols

ProtocolSecuritySpeedUse Case
IPSecHighMediumSite-to-Site
OpenVPNHighMediumRemote Access
WireGuardHighFastModern deployments
Infrastructure

Routers

Layer 3 devices for inter-network packet forwarding

Routers forward data packets between networks by selecting the optimal path based on routing tables and protocols.

Router Functions

Path Selection
Routing Decisions
Packet Forwarding
Data Transmission
NAT / PAT
Address Translation

Routing Protocols

ProtocolTypeUse CaseExamples
OSPFLink-StateEnterprise NetworksLarge organisations
BGPPath VectorInternet RoutingISPs, Large networks
EIGRPHybridCisco NetworksCisco environments
Infrastructure

Network Switches

Layer 2 devices for intelligent frame forwarding within a network

Switches connect devices within a LAN by using MAC address tables to forward frames only to the intended destination port.

Switch Types

Unmanaged
Plug & Play
Home / Small Office
Managed
Full Control
Enterprise
Layer 3
Routing Capable
Advanced networks

Switch vs Hub vs Router

DeviceOSI LayerIntelligenceUse Case
HubLayer 1NoneLegacy networks
SwitchLayer 2MAC address basedLocal network
RouterLayer 3IP address basedBetween networks
Infrastructure

VLANs

Virtual Local Area Networks — logical network segmentation

VLANs allow administrators to logically segment a physical network into multiple broadcast domains without additional hardware.

VLAN Benefits

Security
Isolate traffic
Performance
Reduce broadcast
Flexibility
Logical grouping

VLAN Types

VLAN TypeConfigurationUse Case
Port-basedStatic assignmentGeneral purpose
MAC-basedDynamic by MACMobile devices
Protocol-basedBy protocol typeSpecialised networks

Common VLAN Architecture

Typical Enterprise Setup:
VLAN 10: Management — 192.168.10.0/24
VLAN 20: Staff — 192.168.20.0/24
VLAN 30: Guests — 192.168.30.0/24
VLAN 40: Servers — 192.168.40.0/24