Tools

VoIP VLAN and QoS planner

Last reviewed September 4, 2026

Use this tool to create a starting network plan for one site. Enter the expected voice devices, busiest call count, VLAN and usable link speed.

The result stays in this browser tab. It does not configure a switch, router or phone, and it cannot prove that a provider will preserve your QoS markings.

VoIP VLAN and QoS planner

Create a starting plan for one site. Change the example values to match the busiest expected period. This tool does not configure a switch, router or phone, and your answers stay in this browser tab.

Voice devices at this site

Address growth reserve

Voice VLAN ID

Calls at the same time

Voice bandwidth estimate

Usable site link speed (Mbps)

Can the switches enforce VLAN and QoS rules?

How will phones learn the voice VLAN?

Where will voice traffic be classified or marked?

Is a voice queue ready where the link can become busy?

Change the example values, then build the starting plan.

Planning assumptions

The IPv4 result includes the selected growth reserve and one gateway address. It does not include a local phone system, session border controller or other devices. The voice-capacity result adds a 30% traffic reserve to the selected per-call estimate. Real use changes with packet size, IPv6, encryption, VPNs and tunnels.

Read the result

Voice addresses include the selected growth reserve and one gateway. Add more space for a local phone system, session border controller or other voice devices.
Call capacity is the estimated voice load in each direction, including a 30% traffic reserve. Keep separate capacity for normal data traffic.
Check next lists design choices that still need attention or confirmation.

The smallest calculated subnet is only a starting point. Avoid one very large voice broadcast domain. Large sites normally use several voice VLANs aligned with buildings, floors, switch blocks or failure boundaries.

Apply QoS carefully

RTP marked DSCP EF (46) and SIP signalling marked CS3 (24) are common starting points, not universal rules. Follow the phone-system, switch, router and provider documentation. Trust markings only from managed devices, and test prioritisation while the link is busy.