Embedded Files
CORE DEFENSIVE TECHNICAL SKILLS
Overview
I designed a small business network that uses segmentation, a demilitarized zone for public services, and defense in depth. The design balances usability with strong defaults and clear documentation so it can be operated by a small team. (How to Securly Design Networks)
Objectives
Capture requirements and risk drivers.
Segment users, servers, guests, and Internet of Things devices.
Insert firewalls at trust boundaries and enable monitoring.
Produce diagrams and a configuration registry.
Prerequisites
Working knowledge of routing and switching
Hardware or virtual appliances that support VLANs, ACLs, and next generation firewall features
Tools and technologies
VLAN capable switches and routers
Next generation firewalls, IDS and IPS
Diagramming tool and centralized logging
Implementation
1. Define requirements
Users, applications, compliance needs, expected growth.
Data classification to identify what needs isolation.
2. Design topology
Core: redundant routing and switching.
Segments: Users, Servers, Management, Internet of Things, Guest. Each on its own VLAN and Internet Protocol subnet.
DMZ: public facing services separated from the internal network.
Interconnects: only required flows allowed between segments.
3. Place controls
Firewalls: Internet to DMZ and DMZ to internal, with explicit allow rules.
IDS and IPS: sensors at Internet edge and between key segments.
NAT and egress filtering: restrict outbound traffic to known destinations as needed.
Wireless: separate SSIDs per role with WPA3.
4. Configure devices
Switches: define VLANs and trunk links.
Routers and firewalls: apply ACLs and zone policies based on least privilege.
Servers: harden builds, patch, and restrict services.
VPN: enforce Multi-Factor Authentication for remote users.
5. Monitor and log
Centralize logs from firewalls, servers, and endpoints.
Establish alert rules for policy violations and high value indicators.
6. Document
Produce an annotated diagram with IP ranges, VLAN IDs, and security controls.
Maintain a change record with dates and owners.
Outcomes
A layered architecture that reduces lateral movement and clarifies trust boundaries.
A baseline set of rules and documentation that supports operations and audits.
Skills demonstrated
Network segmentation and policy design
Firewall rule engineering and VPN access control
Documentation of complex systems in plain language
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