Network segmentation is not created by a diagram. It only exists when routing, interfaces, firewall rules, and objects consistently enforce the intended boundaries.
A design may show separate user, server, management, development, and sensitive zones. One broad inter-zone rule can undo much of that protection.
How segmentation weakens over time
- A migration rule allows wider access and is never removed.
- An address group grows until it includes several trust levels.
- Management services become reachable from ordinary user networks.
- Application tiers gain direct access that bypasses the intended inspection point.
- New interfaces or routes create an unexpected alternate path.
- Temporary vendor access becomes permanent.
What to review at each boundary
- Source: Which users, networks, or systems should initiate traffic?
- Destination: Is access limited to the real service endpoint?
- Service: Are only the required ports and protocols allowed?
- Direction: Is reverse or lateral traffic also controlled?
- Inspection: Are logging and security profiles applied where needed?
- Ownership: Who approves and reviews the access?
Test the design against the live configuration
Reviewing segmentation once is not enough. Applications, cloud connections, vendor access, and network objects change. Scheduled review helps identify drift while the reason for the change is still fresh.
Next step: Map your important trust boundaries, then run a ConfigSentry audit to identify broad policies and object definitions that may weaken the design.