Running Microsoft's Netmeeting (to another host running Netmeeeting) to or from a network behind a Netopia that is running NAT can require some additional configuration to allow audio/video sessions.
Below is a list of hardware and firmware loads that this Technical Note is based upon:
| Hardware | Firmware/Version | Interface |
| Netopia 3300 ENT | 8.2 R1 and later | Netopia Menu |
| Netopia 4000 Series | 5.3.9 and later | Netopia Menu |
| Netopia R-Series | 4.8.4 and later | Netopia Menu |
In previous revisions of firmware it was not possible to use the audio/video features of Microsoft's Netmeeting behind NAT. Netmeeting's a/v features places the source address in the data payload, as well as the header. NAT is not able to map incoming traffic with applications that use these types of embedded IP addresses because it does not look at that portion of the packet.
Due to the popular request of Netmeeting, we've created an ALG (application layer gateway) that modifies the source address and ports within the data payload enabling its use from behind NAT in a Netmeeting to Netmeeting type of connection.
Example 1 :
Outbound sessions to remote hosts from workstations behind the Netopia.
Example 2 :
Inbound sessions to hosts behind the Netopia from remote workstations.
Please note that the IP addresses used in the following scenarios are examples only.
In this example you have a workstation or multiple workstations behind the Netopia initiating outbound sessions to remote hosts running Netmeeting.
| Ethernet IP Address of Router: | 192.168.1.1 |
| Ethernet Ip Mask of Router: | 255.255.255.0 |
| Workstation #1's IP Address: | 192.168.1.2 |
| Workstation #1's IP Mask: | 255.255.255.0 |
| Workstation #1's Default Gateway: | 192.168.1.1 |
| Workstation #2's IP Address: | 192.168.1.3 |
| Workstation #2's IP Mask: | 255.255.255.0 |
| Workstation #2's Default Gateway: | 192.168.1.1 |
Both of these workstations will be able to initiate outbound sessions to multiple remote hosts (however, not the same host concurrently). There is a built in ALG (application layer gateway) in the Netopia that will enable users on the internal network to place outbound calls to remote hosts without requiring any specific configuration. We have tested outbound sessions from Netmeeting to Netmeeting hosts only. Other variants may work but have not been tested.
In this example you have a remote workstation that needs to initiate an inbound session to a workstation behind the Netopia.
| Ethernet IP Address of Router: | 192.168.1.1 |
| Ethernet IP Mask of Router: | 255.255.255.0 |
| Workstation #1's IP Address: | 192.168.1.2 |
| Workstation #1's IP Mask: | 255.255.255.0 |
| Workstation #1's Default Gateway: | 192.168.1.1 |
In order to allow an inbound session to a local host, you must create a Server List entry in the Netopia for port 1720. You can follow the instructions in Quick Guide NQG_025 on creating a Server List entry and enabling it in your internet connection profile. It's important to note that the port must be 1720 and not a range, such as 1700-1800.
If you wish to host multiple inbound sessions to workstations behind the Netopia, you must create multiple Server List entries, requiring multiple public IP addresses.
You will need a public IP address per inbound session. You can use a public WAN IP address for the first inbound session to a local workstation. Any additional inbound sessions for further workstations will require additional public IP addresses from your ISP.
For outbound Microsoft Netmeeting's Audio/Video sessions - no specific configuration is required on the Netopia. For inbound sessions - configuring the Server List is necessary to allow remote workstations to initiate sessions to workstations behind the Netopia. This technote addresses Microsoft Netmeeting only. Other audio/video applications may not function through Network Address Translation.