Tutorials · Switching
How to Configure a Voice VLAN and QoS for IP Phones
Give IP phones their own VLAN and priority so calls stay clear even when the network is busy.
Before you start
- A managed PoE switch
- SIP IP phones
- A voice VLAN in your IP plan
Step by step
Create the voice VLAN
vlan 20 name VOICE
Enable voice VLAN on access ports
A PC can connect through the phone while the phone uses the voice VLAN.
interface range gigabitEthernet 0/1-24 switchport access vlan 10 switchport voice vlan 20
Trust phone markings
Phones mark voice packets with DSCP EF (46). Trust them on access ports.
mls qos trust dscpPrioritise voice on uplinks
Place EF traffic in the strict-priority queue on uplinks and the WAN.
Verify call quality
Make test calls during busy hours and check jitter and packet loss on the phone or PBX.
Commands are generic, industry-standard examples. Exact syntax and menu names vary by model and firmware; check your device's manual on the Documentation page.
Pro tips
- Size the Internet upload for concurrent calls (about 100 kbps per G.711 call).
- Use LLDP-MED so phones learn their VLAN automatically.
FAQ
Frequently asked questions
Why do my calls break up?
Usually congestion on the WAN or uplinks without QoS. Prioritise voice and check upload bandwidth.
Keep learning
Related guides
IP telephony solution
Read more →PoE budget guide
Read more →How to Configure VLANs on a Managed Switch
Separate staff, guests, voice and cameras into their own VLANs: create VLANs, set access and trunk ports, and verify traffic separation.
Read more →How to Set Up Inter-VLAN Routing on a Layer 3 Switch
Route between VLANs at wire speed using switch virtual interfaces (SVIs), a DHCP relay and ACLs that control which networks can talk.
Read more →How to Configure Link Aggregation (LACP) Between Switches
Bundle two or more links into one logical link for more bandwidth and redundancy using IEEE 802.3ad LACP.
Read more →Stuck on a step?
Ask Navijin technical support or an authorised partner for help with your configuration.