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Appendix D — Working with Firewalls
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Appendix D — Working with Firewalls
The 5055 SIP phone can be configured to work behind Network Address Translation (NAT)
firewalls which are not SIP aware by enabling the SIP configuration Bypass Firewall NAT
feature and configuring the firewall correctly. To do this:
1. Locate the documentation that came with your NAT firewall and look for instructions on how
to configure a Demilitarized Zone (DMZ) server. You must configure the 5055 SIP phone to
function as a DMZ server to the firewall.
2. Use the 5055 SIP phone configuration web page to:
A. Login to the phone using the web interface and select Network Configuration
Configure a static IP address, Subnet Mask, Gateway, and DNS server address.
Turn DHCP off.
B. Select SIP Configuration. Set Bypass Firewall NAT On.
C. In the "Mode" box select static if the IP of the WAN port of the router never changes.
Select dynamic if the IP changes as the result of DHCP or PPPOE.
D. If you selected static IP in step C., enter this IP in the WAN IP Address field. If you
selected dynamic, enter the URL of the service provider in the "WAN IP Discovery
URL" field.
E. Click the Apply button and verify if Bypass Firewall NAT is still set to On. If dynamic
IP address is used, also verify that WAN IP Address field has been filled in with a
valid address. If Bypass Firewall NAT resets to off, or there is no IP address in the
WAN IP Address field, then there is likely a problem with the WAN IP Discovery
URL that is preventing the phone from obtaining the router’s WAN IP address.
Tip: The 5055 SIP phone must be in a factory-default state (this configuration will not work
with the phone registered or trying to register). To do this power-cycle the phone while
holding down the 3 key and answer “yes” when asked if you want to “use factory
default.”
Tip: There are some service providers that provide free Dynamic IP services. If your Service
provider does not provide this service, you can try either of these:
www.sdforlaget.se/remoteip.asp or
http://www.changeip.com/ip.asp