Has anyone been able to configure the Gateway Bridge to act in a similar way to a Poly Packet Forwarder in that the bridge can send to more than one Network Server but can also accomodate downlinks coming from a particular Network Server?
The sort of example would be a Gateway is configured to point to the Gateway Bridge, The Gateway Bridge is configured to send the packets to two or more Network Servers BUT as well as being able to work with uplink messages the Gateway Bridge can cope with downlink messages coming from one of the Network Servers.
I hope this makes sense!
Please note that the poly packet-forwarder and the LoRa Gateway Bridge are two separate things. E.g. you could use the LoRa Gateway Bridge together with the poly packet-forwarder (where the poly packet-forwarder sends UDP data to multiple endpoints).
The LoRa Gateway Bridge publishes packet-forwarder UDP data over MQTT meaning that you already have the possibility to let multiple network-servers subscribe or publish data over MQTT.
Thanks Orne for your answer - I was aware that they were two separate components - Hopefully MQTT will deal with the route properly.
You can link together more than one MQTT server and subscribe to topics from more than one server 
easy