Effective segmentation starts with identifying what kinds of traffic exist on the network before assigning VLANs — segmenting by device type or department without understanding traffic patterns leads to VLANs that don't actually reduce risk or broadcast noise.

• Corporate data — standard user workstation and application traffic.
• Guest — visitor internet access, isolated from internal resources.
• VoIP — voice traffic, typically prioritized with QoS and isolated from data traffic.
• IoT — cameras, badge readers, building systems, and other low-trust connected devices.
• Servers — production application and infrastructure servers.
• Management — dedicated VLAN for device administration interfaces, isolated from general user traffic.

• Assign a VLAN ID and dedicated subnet to each traffic type identified above.
• Reserve a consistent numbering convention across sites (e.g., VLAN 1xx for corporate, 2xx for guest) to simplify multi-site management.
• Size each subnet to the actual and projected device count for that segment, not an arbitrary default like /24 for everything.
• Document gateway address, DHCP scope (if applicable), and DNS servers for each VLAN.

• Define, per VLAN pair, whether traffic is allowed, denied, or allowed only for specific ports/services.
• Guest and IoT VLANs should default to no access to internal VLANs unless a specific, documented exception exists.
• Management VLAN should be reachable only from designated administrative source addresses, not from general user VLANs.
• Route and firewall policy should be enforced at a Layer 3 device (firewall or routing switch) capable of logging denied traffic.

• Keep broadcast domains small enough that broadcast traffic does not meaningfully impact performance — as a rule of thumb, avoid VLANs sized far beyond actual device counts.
• Consider splitting a large, flat VLAN into multiple smaller ones by floor, building, or function as device counts grow.
• Account for broadcast-heavy protocols (e.g., certain IoT discovery protocols) when deciding how tightly to size a segment.

• VLANs Explained — /knowledge-center/infrastructure/infrastructure-networking/vlans-explained
• Firewalls vs. Routers vs. Switches — /knowledge-center/infrastructure/infrastructure-networking/firewalls-vs-routers-vs-switches