Do nodes keep their ID in the gateway after power cycling / moving around?
Do the nodes keep their ID with the gateway if i power cycle the whole system? I.e. if I've got nodes 1,2,3,4 & 5 and power down the gateway and all of the nodes, remove node 1 and power back up will I just see nodes 2,3,4 & 5 numbered the same? If I reconnect the missing node will it show up as node 1? Is this persistent always? And what if I add 254 nodes, remove 5 then add another 5, does it remap the only spare ID's?
Once a nodeID is assigned using the "Auto"-method, it will be stored in the node's EEPROM and thus never change in the future (apart from options to do this manually). So you do not have to worry about power-loss or removed nodes in the future.
The assignement of the individual ID is done by the controller, so the answer to the second part of your question may vary. FHEM for example will not use "holes" in the numbering of the nodes. Once you are at 254, you have to assign reasonable ID's within the sketch.
Excellent, thanks, just what I needed to know