USG Flex 100H - SIP Trunk - how to open Ports and where to find SIP related settings

DJWindows Posts: 4
First Comment
edited December 2023 in USG FLEX H Series

Hello Experts,

I hope this will be the last question for the next time but I need your help - again.

I need to set up an IP-VoIP-Telephone System connected to the LAN-Port of my USG Flex 100H. The SIP-Trunk is up (initiated by the phone system), outgoing works already. But I'm not able to receive calls.
Here's the setup:

static IP VDSL (93.172.x.y) + Telekom Company Connect SIP-Trunk → USG WAN→VLAN7 (PPPoE) → LAN (192.168.20.x) → ansitel PBX VoIP-system ( / IP phones (192.168.20.x) provisioned in ansitel PBX VoIP-system.

1st: How do I open ports correctly from WAN to ansitel PBX VoIP-system and vice versa?
→ attached to the post there is a picture with the necessary ports/connections (where A is customer-/Zyxel USG-site, B is provider site, "Richtung" means direction)

2nd: Do I have to route/NAT anything?

3rd: Where can I find, enable/disable things like SIP helper/ALG

Again - many thanks in advance!

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