How to organize IP-telephony through VPN?

Question

Telephony

Good afternoon! Our organization has IP telephony consisting of 2 cisco phones, recently it was required to install another IP phone, but already remotely through a VPN tunnel. I connected everything according to this scheme:

The phone connects to the server, and everything seems to be fine, but when you call, the remote phone does not hear the called subscriber (for example, 7001).
Question: Has anyone experienced this and what could be the problem?
I'm new to this, don't be too hard on me.

Answer 1

The ports are closed on the firewall. I don’t know about Cisco, but Asterisk uses port 5060 for connection and the port range is 10000:40000 for conversation.
If you open only one port, then the client will connect, but it will not work.
Determine what ports are needed and open them in the firewall

Answer 2

Let's try to determine if the phone is alive at the network level.
To do this:
- turn off the phone
- install and run the Wireshark program ( www.wireshark.org/download.html).
- start recording the network port to which the phone is connected
- turn on the phone
Start from the device to the port inside the gateway with the line 10.98.90.13= adr and sip
Telephony => VoIP IP Calls => Flow
Watch, save, repeat for the external port of the gateway.
we think we can fix it.