Again, this is straight from the proposed annex:
Upon start-up, each B/IP router shall search its routing table for active entries indicating direct connection via foreign registration with a BBMD. The router shall then proceed to register itself with each such network using the procedures specified in J.5. At the conclusion of all such registrations, the router shall follow the procedure of 6.6.2 in that it shall broadcast an I-Am-Router-To-Network message containing the network numbers of each accessible network except the networks reachable via the network on which the broadcast is being made. Note that networks accessed through a given active UDP port that are not directly connected, but are reachable by means of communication with another B/IP router shall, upon router startup, be deemed to be reachable.
Additional router operations with regard to local and remote traffic shall follow the procedures of Clause 6.
In concept, B/IP devices that are part of an IP multicast group can simply use the IP multicast group address in place of the "local broadcast" address. In this case no BBMDs are required.
It is also possible to mix non-multicast nodes with multicast nodes. In this case a BBMD is required that is also a member of the multicast group. Further details on the use of IP multicast are provided in the proposed Annex J.
That's it then! The next -- and last -- slide summarizes the features of BACnet/IP...