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SonicOS Enhanced 4.0 Administrator Guide
General VoIP Configuration
SonicOS includes the VoIP configuration settings on the VoIP > Settings page. This page is
divided into three configuration settings sections: General Settings, SIP Settings, and H.323
Settings.
Configuring Consistent Network Address Translation (NAT)
Consistent NAT enhances standard NAT policy to provide greater compatibility with peer-to-
peer applications that require a consistent IP address to connect to, such as VoIP. Consistent
NAT uses an MD5 hashing method to consistently assign the same mapped public IP address
and UDP Port pair to each internal private IP address and port pair.
For example, NAT could translate the private (LAN) IP address and port pairs, 192.116.168.10/
50650 and 192.116.168.20/50655 into public (WAN) IP/port pairs as follows:
With Consistent NAT enabled, all subsequent requests from either host 192.116.168.10 or
192.116.168.20 using the same ports illustrated in the previous result in using the same
translated address and port pairs. Without Consistent NAT, the port and possibly the IP address
change with every request.
To enable Consistent NAT, select the Enable Consistent NAT setting and click Apply. This
checkbox is disabled by default.
Note Enabling Consistent NAT causes a slight decrease in overall security, because of the
increased predictability of the address and port pairs. Most UDP-based applications are
compatible with traditional NAT. Therefore, do not enable Consistent NAT unless your
network uses applications that require it.
Private IP/Port
Translated Public IP/
Port
192.116.168.10/
50650
64.41.140.167/40004
192.116.168.20/
50655
64.41.140.167/40745