How to Configure Lancom firewall with 3CX Phone System
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Configuring Lancom with 3CX

Configuring Lancom with 3CX

Introduction

Step 1: Disable SIP ALG

Step 2: Port Forwarding (NAT)

Step 3: Inbound Access List

Step 4: Outbound Access List

Step 5:Validating Your Setup

Introduction

This document describes the configuration of Lancom 1781A devices for use with 3CX. This manual is based on firmware LCOS 9.24 and should be compatible with any device running this firmware. Although settings can be done via Telnet or the web interface, it is recommended to follow the guide via the LanTools and LanMonitor. Please note that we cannot assist you in the configuration of your firewall.

Step 1: Disable SIP ALG

  1. Open the LanTools and navigate to “Configuration → SIP-ALG” and disable it.

Step 2: Port Forwarding (NAT)

  1. To create an inbound access list open “Configuration → IP-Router → Masquerading → Port forwarding table”

  1. Use the “Add” button to set a custom list of ports which shall be allowed to connect to 3CX. All ports and port ranges which needs to be added into this list can be found here. When all ports have been added, click “OK”. Under “Address” add the internal IP of your 3CX.

Step 3: Inbound Access List

  1. Navigate to “Configuration → Firewall/QoS → General” and ensure IPv4-Firewall is enabled.
  2. Click on “Configuration → Firewall/QoS → IPv4-Rules” and create a “Station-Object” 3CXSRV with the internal IP of 3CX.
  3. Click on “Service-Object” and create a set of rules similar to Step 2 with the ports and transports as seen below. Update the 3CXMNG-Port according to your installation port.

  1. Finally click on the “Rules” button and create the rules using the service objects you created in the previous step.

Step 4: Outbound Access List

Since a Lancom router does not block any outgoing packets in the basic setting, no rules need to be set up. If there is a general rule for blocking or only certain packages should be allowed duplicate the inbound rule list for outbound.

Step 5:Validating Your Setup

Log into your 3CX Management Console → Dashboard → Firewall and run the 3CX Firewall Checker. This will validate if your firewall is correctly configured for use with 3CX.
More information about the Firewall Checker can be found
here.

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