Yealink SIP-T23P [616/841] Procedure

Administrator’s Guide for SIP-T2 Series/T19(P) E2/T4 Series IP Phones

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In the VoIP environment, NAT breaks end-to-end connectivity.

NAT traversal is a general term for techniques that establish and maintain IP

connections traversing NAT gateways, typically required for client-to-client networking

applications, especially for VoIP deployments. STUN is one of the NAT traversal

techniques supported by IP phones.

STUN (Simple Traversal of UDP over NATs)

STUN is a network protocol, used in NAT traversal for applications of real-time voice,

video, messaging, and other interactive IP communications. The STUN protocol allows

applications to operate behind a NAT to discover the presence of the network address

translator, and to obtain the mapped (public) IP address and port number that the NAT

has allocated for the UDP connections to remote parties. The protocol requires

assistance from a third-party network server (STUN server) usually located on public

Internet. The IP phone can be configured to act as a STUN client, to send exploratory

STUN messages to the STUN server. The STUN server uses those messages to determine

the public IP address and port used, and then informs the client.

SIP and TLS Source Ports for NAT Traversal

You can configure the SIP and TLS source ports on the IP Phone. Previously, the IP phone

used default values (5060 for UDP/TCP and 5061 for TLS). In the configuration files, you

can use the following parameters to configure the SIP and TLS source ports:



Local SIP Port



TLS SIP Port

If NAT is disabled, the port number shows in the Via and Contact SIP headers of SIP

messages. If NAT is enabled, the phone uses the NAT port number (and NAT IP address)

in the Via and Contact SIP headers of SIP messages, but still use the configured source

port.

Procedure

NAT traversal and STUN server can be configured using the configuration files or locally.

Configuration File

<y0000000000xx>.cfg

Configure NAT traversal and

STUN server on a phone basis.

Parameters:

sip.nat_stun.enable

sip.nat_stun.server

sip.nat_stun.port

Configure local SIP port and TLS