just installed the Zyxell modem; turned off the firewall features;
unticked the DHCP option 125
This is the sole & main router in the network
All my voip phones continue to work but my work phone; which I guess is more "secured" (not too sure but I think its tls 1.2)
It simply wont register (its got an IP just fine, I can ping 126.96.36.199 with the built in tool, etc.)
If i replace the router with my good old DIR-825 running DD-WRT;
all is well.
Problem is my dir825 is quite old, and wanted to leverage better Wifi performance of the Zyxell.
Any ideas ?
Solved! Go to Solution.
1. Login to the Zyxel router admin panel.
2. Click on "Expert mode".
3. On the left hand side of the window, click on the Settings button (small gear icon).
4. Under the Network section, click on "NAT".
5. Click on the "Port Forwarding" tab.
6. In the Service Name drop down box, select "VoIP (SIP)".
7. In the "Server IP Address" drop down box, select the IP corresponding to the VoIP device.
8. Click on "Apply".
If it doesn't seem to work, try rebooting the router and your VoIP phone should be functional once it comes back online.