Yealink T46G Administrator's Manual page 276

Yealink Skype for Business HD IP Phones Administrator Guide
To configure IPv6 static DNS when DHCP is used via phone user interface:
Press Menu->Advanced (default password: admin) ->Network->WAN
1.
Port->IPv6->DHCP.
Press
2.
Enter the desired values in the Primary DNS and Second DNS fields respectively.
3.
Press the Save soft key to accept the change.
4.
The Skype for Business phone reboots automatically to make settings effective after a
period of time.
262
or , or the Switch soft key to select Enabled from the Static DNS field.