Network design is the structured process of planning a computer or industrial network to meet a business’s connectivity, performance, security, and scalability needs. Whether you’re building a new office LAN, upgrading an industrial plant network, or architecting multi-site connectivity, a well-designed network is essential for reliability, uptime, and security.

Network design outlines the topology, hardware, protocols, and services that define how data flows between devices and locations. It considers both the logical (IP addressing, VLANs, routing) and physical (cables, switches, Wi-Fi) aspects of the infrastructure.

<ol><li>Requirements Gathering<ul><li>Number of users/devices</li><li>Type of applications (VoIP, SCADA, video, ERP)</li><li>Security/compliance needs (e.g., PCI, HIPAA, ISA/IEC 62443)</li><li>Growth expectations (scalability)</li></ul></li><li>Topology Planning<ul><li>Choose between star, mesh, hybrid, or ring topologies</li><li>Determine physical layout (floor plans, cabinet locations)</li></ul></li><li>IP Addressing & VLANs<ul><li>Subnetting and addressing plan</li><li>Segment by department, device type, or function (IoT, guest, servers)</li></ul></li><li>Hardware Selection<ul><li>Switches (Layer 2/3), routers, firewalls, access points, cabling</li><li>PoE for access points and IP cameras</li><li>Redundancy with stacked switches or failover routers</li></ul></li><li>Security Architecture<ul><li>Firewalls, DMZ, VPNs</li><li>Network segmentation</li><li>NAC (Network Access Control) and endpoint policies</li></ul></li><li>Wireless Planning (if applicable)<ul><li>Heat mapping for AP placement</li><li>Band/channel selection, roaming, security (WPA3, enterprise auth)</li></ul></li><li>Monitoring & Management<ul><li>SNMP-enabled devices</li><li>Centralized tools like SolarWinds, PRTG, Zabbix</li><li>Syslog and NetFlow/traffic analysis</li></ul></li><li>Documentation & Testing<ul><li>Create detailed diagrams</li><li>Verify throughput, redundancy, failover paths</li></ul></li></ol>

Network Type	Purpose	Example
LAN	Local network for a single building/floor	Office, school, warehouse
WAN	Connects multiple sites	Branch offices or factories
WLAN	Wireless LAN for mobility	Campus Wi-Fi
Industrial Ethernet (OT)	Connects PLCs, HMIs, SCADA devices	Factory or plant floor
Data Center Network	Handles high-throughput server/storage links	Virtualized environments

Enterprise Three-Tier Model:<ol><li>Core Layer: High-speed backbone connecting buildings/sites</li><li>Distribution Layer: Aggregates and segments traffic</li><li>Access Layer: User devices, printers, cameras connect here</li></ol>

<ul><li>Use redundant paths and power (UPS) for critical devices</li><li>Implement 802.1X for device authentication</li><li>Keep management traffic separate (e.g., VLAN 99)</li><li>Monitor and update firmware and configurations regularly</li><li>Document everything: IP maps, rack layouts, config backups</li></ul>

<ul><li>Cisco Packet Tracer, GNS3 – for simulation</li><li>NetBox – IPAM and documentation</li><li>SolarWinds Network Topology Mapper</li><li>Ekahau or NetSpot – for wireless heat mapping</li></ul>