Chapter 11 Napt; Section 1 Napt; Figure 11-1 Napt Configuration Example - NEC Sl2100 Networking Manual

NAPT
S 1 NAPT
ECTION
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.
IP Phones connected via NAPT
SL1100
192.168.1.10/24
192.168.1.1 (Gateway)
192.168.1.11 (VoIP Gateway)
1.1.1.1
Public IP
Public IP
192.168.4.1/24
192.168.4.2/24
IP Phone
Networking Manual
VoIP Gateway RTP = 10020 RTCP = 10021
192.168.1.2/24
NAPT
Router
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

Voice for a call is sent to Public IP
Address 1.1.1.1.
ports 10020~10083.
11
11-1