System information

System Administration Guide

300 Main Street • East Rochester, NY 14445 • Toll Free 1-866-ALLWORX • 585-421-3850 • www.allworx.com

Revised: March 28, 2007

Page 65

4. Modify the Phone Options to change the RTP Media Port Range parameter to reduce the maximum

range.

5. The next step is to modify the NAT firewall configuration of the 3

party firewall. You want a one-to-one

map of each of the RTP ports through the firewall such that packets arriving at those ports on the

firewall’s WAN interface are routed to the phone that is inside the NAT firewall. The directions for doing

this are unique to each NAT firewall product and therefore beyond the scope of this description.

6. Configure the handset to use a static address on the LAN. Mapping of ports to a dynamically addressed

phone will cause problems should the address of the phone change as a result of a network outage or

power loss.

An alternative solution to this problem is to always route audio through the common Allworx server that both

remote phones are associated with. In the Servers / VoIP Server / Modify options if the Force Remote Phone

Audio through the Server option is checked, this should also resolve the problem. However, significantly

additional latency may be present in the call and result in unacceptable audio quality.

Calling through ITSPs

Internet Telephony Service Provider (ITSP) services configured on the Allworx

server may not be accessible

from remote phones that are behind NAT firewalls.

Solution: Statically map (one to one) the remote phone’s RTP ports through the NAT firewall. This requires

the same steps as described in the different remote sites phone limitation above.

14.4 Remote 3

Party

IP Phones

In addition to support for the Allworx

IP phones, the Allworx

server supports 3

party remote SIP phones as

well. Steps for configuring these are unique to each phone model and brand. However, any of the fully RFC

compliant SIP phones than work on the LAN side of an Allworx server typically can be made to work as a

remote phone.

Note: The configuration steps can be much more involved and are more challenging to get to work when

they are behind other 3

party firewalls. Generally speaking, Allworx recommends using only Allworx

IP phones as remote devices.