Yealink SIP-T2 SERIES Administrator's Manual page 758

Administrator's Guide for SIP-T2 Series/T19(P) E2/T4 Series/CP860 IP Phones
sip.nat_stun.port = 3478
Note: If you change this parameter, the IP phone will reboot to make the change
take effect.
Web User Interface:
Network->Advanced->NAT->STUN Port(1024~65000)
Phone User Interface:
Menu->Settings->Advanced Settings (default password: admin)
->Network->NAT->Port
account.X.nat.nat_traversal
Description:
Enables or disables the NAT traversal for account X.
0-Disabled
1-STUN (Enabled for SIP VP-T49G)
X ranges from 1 to 16 (for SIP VP-T49G/SIP-T48G/T46G/T29G)
X ranges from 1 to 12 (for SIP-T42G)
X ranges from 1 to 6 (for SIP-T41P/T27P)
X ranges from 1 to 3 (for SIP-T40P/T23P/T23G)
X ranges from 1 to 2 (for SIP-T21(P) E2)
X is equal to 1 (for SIP-T19(P) E2/CP860)
Note: It works only if the value of the parameter ―sip.nat_stun.enable‖ is set to 1
(Enabled).
Web User Interface:
Account->Register->NAT
Phone User Interface:
Menu->Settings->Advanced Settings->Accounts->AccountX->NAT Status
account.17.nat.nat_traversal
Description:
Enables or disables the NAT traversal for IP call.
0-Disabled
1-Enabled
Note: It works only if the value of the parameter ―sip.nat_stun.enable‖ is set to 1
(Enabled). It is only applicable to SIP VP-T49G IP phones.
Web User Interface:
Account->SIP IP Call->NAT
736
Parameters Permitted Values
0 or 1
0 or 1
Default
0
0