Chapter8. SIP Services
Selecttwo IP addresses out of the ones assigned to the Telecommuting Module under Directly Connected
Networksand 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

Enterthe ports to use for the STUN server. These ports, on the IP addresses selected, will not be available for
anythingelse.
Remote NAT Traversal
Ifyour SIP client is not STUN-capable, you can use the built-in Remote NAT traversal feature of the
TelecommutingModule. The client must register on the Telecommuting Module (or through it).
TheSIP client needs to re-REGISTER rather often for this to work. The exact period for this depends on the
NAT-ingdevice,but 20 seconds should be enough to get across most NAT boxes. It is not advisable to use
OPTIONSfor 3Com SIP clients.

Remote NATtraversal

Turnthis function on or off.

Re-REGISTER period for clients

Clientsusing this function will have to re-REGISTER very often, to keep the IP/port NAT binding. A
re-REGISTERinterval of 20 seconds should be enough to ensure this.
Ifsome clients are unable to handle short re-REGISTER intervals, the Telecommuting Module can send OPTIONS
messagesinstead, see below.

Use OPTIONS for registered clients

Selectif the Telecommuting Module should use OPTIONS packets instead of short re-REGISTER intervals to keep
theNAT binding.
OPTIONSshould not be used for 3Com phones, as they don’t respond to that.

OPTIONS interval

Enterthe interval for the Telecommuting Module to send OPTIONS packets to the client.
Save
Savesthe Remote SIP Connectivity configuration to the preliminary configuration.
Cancel
Revertsall of the above fields to their previous configuration.
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