Re: [Bacnet-developers] DNET and gateway

[Dave L. <da...@po...>]

Hi Derek,

Take me with a grain of salt...   I know quite a bit about bacnet over IP but haven't spent extensive time setting up systems...

I suppose you set it up that way presuming the BBMD is on your current subnet.   Then you wouldn't need to explicitly handle BBMDs I suppose.

But you are using multiple device objects routed at the same IP?   With the root device being DNET 0 and the rest of them being DNET 2809?   I don't think you should program the DNET of 2809 into the BBMD.   I think what should be happening is you get the WHOIS broadcasts at the default DNET (0) and the bacnet stack does some work to make sure all the device objects  get it, since it is broadcast it can do that lol.    But the broadcasts will come in PTP as forwarded broadcast messages.

And of course responses should have the appropriate SNET set.

Not sure at this point if we had to make a modification to make it do either of those things though.   I know I modified that code, just cannot remember why...

From: Derek Noffke <de...@pu...>
Sent: Thursday, May 13, 2021 10:40 AM
To: 'Discussion for developers of the BACnet stack' <bac...@li...>
Cc: Dave Lindauer <da...@po...>
Subject: RE: [Bacnet-developers] DNET and gateway

Thanks Dave,

I know very little about BBMD workings so any info is most welcome.  :)

Client on site manually adds my root device 2700000 to his BBMD.
Discover works 20% of the time.
Client says problem is 2700000 is on DNET 0 while all other are on DNET 2809

Regards,

Derek Noffke
PurpleSwift
Cell: 082 780 4680
Tel: 021 761 8264



From: Dave Lindauer via BACnet-developers [mailto:bac...@li...]
Sent: Thursday, 13 May 2021 16:15
To: Discussion for developers of the BACnet stack
Cc: Dave Lindauer
Subject: Re: [Bacnet-developers] DNET and gateway

Generally the BBMD you want to talk to is on some other subnet.   To be compatible with a BBMD you have to register with it at intervals (the registration expires) so that you can get broadcasts from the other subnet.    Also in addition to broadcasting on your own network, you have to send your broadcasts directly to the BBMD in point to point fashion so that they can be received on the other network.   For example the IAM messages.

There is specific protocol related to this, but the bacnet stack has helpers and so forth.    There might be an example as well.    I found it pretty easy not only to interact with BBMDs but to create one for testing!

David
From: Derek Noffke <de...@pu...<mailto:de...@pu...>>
Sent: Thursday, May 13, 2021 8:59 AM
To: bac...@li...<mailto:bac...@li...>
Subject: [Bacnet-developers] DNET and gateway

Greetings,

I have an app based on the gateway demo code.  BACnet Stack Version 0.8.4
I have been informed that my gateway is not compatible with a BBMD.

The startup I-AM sequence is attached.
I see that the I-AM for my "root" device 2700000 does NOT contain the DNET.
Is this possibly the problem?

Regards,

Derek Noffke
PurpleSwift
Cell: 082 780 4680
Tel: 021 761 8264