Smoothwalls running a release or update earlier than Kenilworth will find Viber is not working, or only working partially. After a few rings, viber will say it has answered, and will hang up the call.
How do I allow Viber through the Smoothwall?
Create a firewall rule(s) that allow the following ports;
See https://help.smoothwall.net/Hearst/Content/modules/rule/cgi-bin/rule/sourcerules.htm for pre-Inverness customers; or https://help.smoothwall.net/Inverness/Content/ui/admin/ipfilter/forward.htm for customers running Inverness or higher.