The Milight bridges (old and new) respond to specific network packets.
That is how auto discovery is implemented.
For the old bridges this response is also used as a “heart-beat” to know if a bridge is still online.
The new bridges require to establish a “network session” with their own heart-beat function. That means,
the bridge can still work in OpenHAB even if the auto-discovery failed (probably because the receiving port is blocked by a firewall).
Unlike many suggested, the Milight bridge does not need a static IP. The binding figures out if the bridge IP changed and re-establish a new session. Unfortunately there is still a bug in the binding that I couldn’t find time to resolve yet. Every time a new session is established (which happens automatically after a day or so), the old session was kept as well. After a certain time the bridge is bombarded by network packets from all those active sessions and will eventually fail.
I really hope I can find some time for this issue.