Inter-Tel AXXESS Manual page 1546

Appendix F – Network Topology
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INTER-TEL AXXESS
4.
5.
6.
10.6 Incorrect configuration may result in an undesirable effect called tromboning (also
known as "hairpinning"). Not all firewalls support tromboning, so avoid this configuration, if
possible. The following diagram illustrates tromboning.
10.7 Automatic NAT Detection: Automatic NAT detection is a method by which the
Axxess and IP endpoint can communicate to determine whether the IP endpoint is inside the
firewall (NAT) on the internal network or outside the firewall (NAT) on the Internet. This auto-
matic capability is necessary for mobile IP endpoints that move between the internal network
and the Internet. (This is a common scenario for the Model 8602 IP softphones). Note that this
automatic detection capability is limited to IP endpoints in ITP mode; it does not apply to IP
gateway trunks.
10.8 Under extremely rare scenarios, NAT autodetection might improperly detect a native
condition instead of a NATed condition (possibly resulting in consistent one-way audio). If this
situation occurs, contact technical support for further information to prevent this scenario.
Page F-16
MANUAL VERSION 11.0 – May 2008
In the System\Devices and Feature Codes\Stations\Local\<extension>\IP Settings folder
for the newly created IP endpoint from the Internet, set the NAT Address Type (Native,
NAT, or Auto). The default is set to Auto.
Configure the IP endpoint (that is on the Internet) to communicate with the IPRC (pub-
lic) NAT address. You can do this through the IP endpoint setup sequence or through
the IP endpoint Web page. The address to use is the public address associated with the
IPRC IP address.
For SIP gateways only, you must also program the System NAT IP Address field (in
System\IP-Related Information) and the SIP Gateway Name field (in System\Trunk-
Related Information\SIP Gateways).
Endpoint Configurations for Native, NAT, and Auto NAT Types