BACnet BBMD over OpenVPN

NETWORKING SOLUTIONS
1

Hello everyone.

I’m trying to connect Siemens PLC which is communicating via BACnet<>LON router. I have OpenVPN connection to Teltonika and I’m able to fetch BACnet objects from the router itself but not from the PLC using port forwarding rules.

Here is my topology:

image
image740×140 45.1 KB

With just port forwards I can fetch the PXG80-n router’s BACnet object but I can’t fetch the PLC’s objects. Here is port forwarding settings:

image

And this is the result with foreign device registration in Yabe:

image
image310×102 15.9 KB

I was wondering if I’m able to solve this with router’s BACnet service, but I have no clue how to set it up.

3

Hello,

If you’re using a VPN setup, you don’t need BBMD or foreign device registration, thus BBMD should be disabled.

A couple of points to check:

  • What is the LAN IP of the device running Yabe?
  • In your port forwarding rule, there’s no internal port specified. It should be pointing to 47808.
  • If there’s only one BIP interface configured for the BACnet router, you would also need another one for the VPN setup.

Could you please clarify your topology (including all IP assignments) and BACnet configuration screenshots?

Best regards,

4

Hello,

Thanks for the reply.

  • Yabe is running on my laptop and there is nothing connected LAN and it using dhcp. Yabe’s local endpoint is 10.100.16.10.
  • Yes, I chose “No rewrite” to internal port so it is using same port as external, right? This works with devices that use direct communication, but not if communicating through BBMD device (Can read the objects from BBMD device itself but not the other like the LON device in this case).
  • What of these (eth0, eth0.1, eth0.2, br-lan) is used for VPN then?

Here is picture of the BACnet settings in RUT right now. I’ve tried all kind of combinations but haven’t got it working. How should settings look like?

image
image1555×1006 36.8 KB

5

Hello,

As your setup is pretty complex and complicated, a few clarifications would be helpful to better understand it:

  • What exactly is 192.168.0.3 in your network, is it the PLC?
  • Does the eth0.2 interface actually have an IP assigned to it?
  • Just to mention, BACnet is currently not enabled in the general configuration.

Could you also share what interfaces/devices are available when creating a BIP interface under the BIP configuration? Port 47808 is correct for BACnet/IP.

In short, you’ll need to create two BIP configurations: one for the VPN interface (check the OpenVPN interface name with ifconfig) and one for the local network (typically br-lan or eth0.1, depending on where the BACnet PLC is connected).

If there’s no VPN interface displayed in BIP configuration, then it might need to be added via CLI by editing the /etc/config/bacnet_router configuration to specify it under the config port '2' section.

Additionally, for this type of setup, a TAP style VPN might be necessary to properly broadcast UDP traffic through BACnet communication. If possible, consider testing it with VPNs like ZeroTier or Tailscale.

Best regards,