NAPT
SECTION 1 NAPT
1.1 Introduction
NAPT, or Network Address Port Translation, is a method by which a private address (or addresses)
and their TCP/UDP ports are translated into a single public address and its TCP/UDP ports. In the
case of IP phones with the SL2100 it allows their connection to a public (Internet) IP address which is
then converted back to the private (non-Internet) IP address on the customer’s network. The
translation is available at the SL2100 end as well as at the remote IP Phone end of the connection if
required.
SL1100
192.168.1.10/24 VoIP Gateway RTP =
10020
RTCP =
10021
192.168.1.1 (Gateway)
192.168.1.11 (VoIP Gateway)
IP Phones connected via NAPT
192.168.1.2/24
NAPT
Router
1.1.1.1
Public IP
Public IP
192.168.4.1/24
192.168.4.2/24
IP Phone
Voice for a call is sent to Public IP
Address
1.1.1.1.
ports
10020~10083.
Port Forwarding
in this router should be set
as follows.....
UDP ports
5080~5081
to
192.168.1.10
UDP ports
10020~10083
to
192.168.1.11
Port Forwarding
in this router (if necessary) is
as follows.....
UDP ports
5060
to
192.168.4.2 (IP Phone control)
UDP ports
3462
to
192.168.4.2 (IP Phone Voice)
Figure 11-1 NAPT Configuration Example
Networking Manual
11-1
NAPT
11
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