MOTOTRBO IP Networking Requirements

MOTOTRBO utilises a proxy discovery mechanism to learn about the network. All Peers (Repeaters, RDAC, 3rd Party Applications) initially communicate with the Master and then learn of the rest of the system. When a Peer joins the Master, the Master will inform the newly joined Peer about any other peers on the network, and then informs the other Peers about this newly joined Peer. This mechanism allows all of the Peers in the network to communicate directly with one another.

This information consists of the IP address and port used by all Peers in the system and is retrieved by Master from the messaging the Peer sends when requesting to join the system. Therefore the addressing that the Master sees with respect to a peer must be the same addressing that any device in the system can use to contact that peer.

The above discovery mechanism allows for easy system installation but puts specific requirements on the IP topology based on the system type. Below is a list of MOTOTRBO systems and their IP topology requirements based on the network location of the Master with respect to the network location of any peer.

NB! As of release 2.2, NAT Loopback is no longer a requirements for the Routers used in Linked Capacity Plus.

The Hair-Pinning/NAT-Loopback feature allows for a message from a LAN IP address, destined for the WAN IP address of a router, to be transmitted back into the LAN after going through the Firewall and NAT rules of the router. Therefore a local message will appear to have come from the WAN.

System Type	Which is the Master?	Which are the Peers?	System Topology	Type of IP Routing Required
IPSC	One repeater	Other Repeaters, RDAC, Third Party Applications	All Repeaters in the same subnet behind the same router	Basic LAN
			Master and another Peer behind a single subnet with other Peers in a different subnet	Hair-Pinning/NAT-Loopback required in the router that creates the subnet where the Master resides. Full Cone NAT support required across IP topology.VPN Tunnel can be used to flatten out the topology
Capacity Plus	One repeater	Other Repeaters, RDAC, Third Party Applications	All Repeaters in the same subnet behind the same router	Basic LAN
			Master and another Peer behind a single subnet with other Peers in a different subnet	Hair-Pinning/NAT-Loopback required in the router that creates the subnet where the Master resides. Full Cone NAT support required across IP topology.
Linked Capacity Plus	One repeater (The master supports two IP interfaces and acts both as a Master and as a "virtual" peer)	Other Repeaters, RDAC, Third Party Applications	Master and its site peers behind a single subnet while other sites reside behind another subnet.	Hair-Pinning/NAT-Loopback required in the router that creates the subnet where the Master resides. Full Cone NAT support required across IP topology. Note: To qualify a router for LCP – follow Router compatibility test procedure for LCP system.
Underlying Requirement	The IP/Port addressing that the Master sees with respect to a peer MUST be the same addressing that ANY entity in the system can use to contact the peer if it is required to do so.

Also see my posts MOTOTRBO and IP and Linked Capacity Plus Router Configuration.