- Model: P-Series
- Firmware version: Any
- Phone: Grandstream GXP, GRP models
By default the Grandstream phones will take all the codecs which will cause MTU issue. The phenomenon of issue that the user unable to make calls, but he is able to receive calls.
Due to a special config file rule, the provisioning work could not remove the phone's default codecs by sentence in the config file. We have to remove the codecs manually as the following procedure.
To overcome the MTU issue, you can also choose the TCP registration solution which is more efficient, see the guide: How to Register Extension by TCP on P-Series
1. Go to Auto provisioning menu
If your phone has been provisioned by Yeastar P-series PBX, then execute this step.
Or skip this step.
Choose the phone you need and only leave 2 codecs PCMU and PCMA available.
2. Login the phone's web GUI to configure codecs
Set the codec 3 -8 all as PCMA.
Click Save and Apply.