Troubleshooting VoIP service over a non-CenturyLink ISP
If your Hosted VoIP service is not working and you're using a non-CenturyLink ISP (alternate carrier), try these tips:
Some routers allow for plug and play setup of VoIP phones, but not all routers are built the same. Due to the number of routers available with other providers, CenturyLink does not test, certify, or provide configurations for these devices.
You should always back up your router configuration before making changes. CenturyLink repair cannot assist with this activity.
If your router supports SIP ALG, try turning that feature off.
DMZ (demilitarized zone) is a feature on most routers where it will direct all traffic from the internet to a particular device on the network. Try pointing your DMZ to your Hosted VoIP phone.
Features like busy lamp field and shared call appearances might not function properly depending on your Internet provider’s router settings.