Yealink SIP-T54S Administrator's Manual page 139

Select STUN/Manual NAT from the pull-down list of NAT.
3.
Click Confirm to accept the change.
4.
To configure local SIP port and TLS SIP port via web user interface:
Click on Settings->SIP.
1.
Enter the desired local SIP port in the Local SIP Port field.
2.
Enter the desired TLS SIP port in the TLS SIP Port field.
3.
Click Confirm to accept the change.
4.
Setting Up Your System
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