Trisul's Blog

After 20 years in networking, if there’s one principle I never compromise on, it’s network segmentation. In the modern IT landscape—where threats are everywhere and complexity is the enemy—using VLANs to segment your network is not just best practice, it’s essential.

What is Network Segmentation?

Network segmentation is the practice of dividing a network into multiple isolated segments (or subnets). VLANs (Virtual Local Area Networks) are the most flexible and scalable way to do this on Ethernet networks. Each VLAN acts as a separate broadcast domain, even if devices are physically on the same switch.

Why Segment? Three Real-World Reasons

1. Security: Segmentation limits the “blast radius” of any attack. If malware or an intruder gets into one VLAN, they can’t easily access devices in others. For example, keep IoT devices or guest WiFi on their own VLAN—never let them touch your business-critical systems.
2. Performance: Large flat networks get bogged down with broadcast traffic. VLANs keep things efficient and reduce unnecessary chatter, which is crucial as your network grows.
3. Compliance & Policy: Many regulations (HIPAA, PCI-DSS) require isolation of sensitive data. VLANs make it straightforward to enforce these boundaries and audit your network.

How I Approach VLAN Design

• Start with a Plan: Map out departments, device types, and trust levels. Each should have its own VLAN.
• Use Meaningful VLAN IDs and Names: e.g., 10 - Staff, 20 - Servers, 30 - Guests.
• Implement Inter-VLAN Routing Carefully: Use firewalls or Layer 3 switches and apply strict ACLs (Access Control Lists) so only necessary traffic flows between VLANs.
• Document Everything: Keep a record of VLAN IDs, subnets, and purposes. This saves hours during troubleshooting or audits.

Pro Tips from the Field

• Never let printers or IoT devices on your main VLAN. They’re often the weakest link.
• Use “default deny” rules between VLANs. Only open what’s needed.
• Test segmentation regularly. Use tools like ping and traceroute to ensure isolation is effective.
• Automate VLAN assignments with 802.1X where possible. This adds security and reduces manual errors.

The Bottom Line

In 2025, with ransomware, insider threats, and remote work, network segmentation is your first and best line of defense. VLANs are not just for big enterprises—they’re for any business that values security, performance, and peace of mind.

Want a VLAN design review or help with segmentation? Reach out—let’s make