Administrator's Guide

Chapter 10. SIP Services
does not do STUN (or if the STUN-capable client is located behind a Symmetric NAT de-
vice), you have to use the Remote NAT Traversal feature. This is easier for the client, but
generates more network traffic for the Telecommuting Module.
The settings on this page are only available when the Remote SIP Connectivity module has
been installed.
STUN Server
Use the STUN server if you have STUN-aware SIP clients. You will need at least two public
IP addresses to make it work with all client implementations of STUN.
STUN will not work properly if the NAT device uses Symmetric NAT (where the client’s
private IP/port pair translates to different public IP/port pairs depending on destination, and
where computers other than the destination host are not allowed to reply on that IP/port pair).
The client also needs extra configuring for this; it must know which IP addresses and ports
the STUN server has.
STUN server
Select if the STUN server should be switched On or Off.
STUN server IP addresses
When activated, the STUN server requires two IP addresses, and a pair of ports on these two
IP addresses, on the Telecommuting Module. STUN clients will then send test packets to
these ports.
Select two IP addresses out of the ones assigned to the Telecommuting Module under Di-
rectly Connected Networks and Alias on the interface pages.
Note: for the STUN server to work properly, you need to select IP addresses which the
clients can reach. In normal circumstances, this means that only public IP addresses can be
used.
STUN ports
Enter the ports to use for the STUN server. These ports, on the IP addresses selected, will
not be available for anything else.
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