Mitel MIVOICE OFFICE 250, Installation And Administration Manual, Page: 461 / 585

Network IP Topology
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6. For the “internal” IP phones (those in the internal network with private addresses), set the NAT
address type Native , and configure the IP phones to communicate with the Base Server (private)
internal address, 192.168.1.2. 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.
Base Server with a PEC-1
To set up Near-End NAT Traversal for IP Phones on a Base Server with a PEC-1:
1. Configure the firewall/NAT device for a static mapping for the IP address of the Processor
Expansion Card. This associates a public IP address with the native address of the Processor
Expansion Card (PEC-1).
2. In the DB Programming IP Connections folder, program the NAT IP Address to be the public
address that was associated with the native private address in
step 1
.
IMPORTANT
Configure the firewall security settings for the newly mapped IP address(es) as
described in “Port Usage and Protocols” on page 442. Depending on how the
particular firewall defaults its security, failure to configure the security may result in
no-audio conditions or security vulnerabilities.