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VOIP Setup


I'm new to this organization and their cisco switch setup is giving me a headache.

we have Voip setup with vlans and all, but the ports carrying voip have been set as trunk ports. I want to make them normal access ports that can carry voice traffic. But whenever i do so, the phones refuse to register.

This is the current setup of a voip port:

interface GigabitEthernet1/0/10
switchport trunk native vlan 21
switchport trunk allowed vlan 20,21
switchport mode trunk
switchport voice vlan 20
spanning-tree portfast


This is what I did:

no switchport trunk native vlan 21
no switchport trunk allowed vlan 20,21
switchport mode access

switch access vlan 21
switchport voice vlan 20


But it shows phone unregistered.

VLAN 21 = data vlan

VLAN 20 = voice

the native vlan on the real trunk link is vlan 1

why does it work when the interface is a trunk but doesnt work when i change it to my configuration?


Switch is a cisco 2960 and IP phone is a CP 7821

1 Accepted Solution

Accepted Solutions

Adam Pawlowski

Not all platforms support voice VLAN functionality without specifying the port mode is trunk. For some it's just an advertisement and needs configuration, and for others it configures it to accept that tagged traffic.

If what you've changed it to doesn't produce anything useful then configure it back the way it was.

View solution in original post

8 Replies 8

Leo Laohoo
VIP Community Legend VIP Community Legend
VIP Community Legend

There are a few VoIP brands that need be on Trunk ports.