Thank you for asking this question in the support community.
To verify the unit has the Voice Feature Pack (VFP) loaded, you will have to login. You can do this via the web interface (GUI) or the command line (CLI).
From the GUI the System Summary page will show the "Firmware Version." If the firmware version ends in "V" then the unit has the VFP loaded. If it does not end in "V," then it is the standard feature pack (SFP) or enhanced feature pack (EFP).
From the CLI issue the command show version. Then the first line will show the firmware version. If it ends in "V" then the unit has the VFP loaded.
# show version
ADTRAN, Inc. OS version R.10.5.0.V
I hope that makes sense, but please do not hesitate to reply if you have any additional questions.
Indeed, I have the VFP.
ADTRAN, Inc. OS version R10.5.0.V.
Sometimes the PBX sends SIP messages that the NV cannot understand because they aren't not implemented, but those messages aren't not quite big deal for the end points to work correctly.
Do you have a packet capture of the Registration process?, I suggest you to capture one to see to which options the NV is responding with the 501 error.
Seems that is rejecting the REGISTER message, one question here:
Are you trying to register a phone in the Adtran unit?, because according to the Adtran documentation I think it's not possible to work as a B2BUA, the equipment it will only handle that the communication allow the unit and your PBX works correctly.
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