ScreenOS Firewalls (NOT SRX)
ScreenOS Firewalls (NOT SRX)

Need help with VoIP through SSG5 behind cable modem, dynamic IP

‎08-03-2015 08:24 PM


Hi all,

seems like a pretty common scenario, but it doesn't work 😞

SSG5 is meant to connect to cable modem, which dishes out public IP addresses via DHCP.


In the TRUST zone, I have a bridge group and have static DHCP reservation for Sipura (Linksys) 2100.


The setup looks like this:


CABLE MODEM <-> SSG5 <-> Sipura 2100 <-> Desktop


When I plug a desktop into LAN side of Sipura 2100, I have internet browsing and Skype works.

But making a call through Sipura 2100 doesn't happen.


Sipura 2100 works well when setup is uplinked directly to cable modem (only one LAN port 😞 )


I don't know how to configure NAT because I have dynamic IP for WAN in the "UNTRUST" zone?


If anyone has a configuration example, would be much appreciated.

Or if you can describe, since I'm not too good with ScreenOS CLI anyway.