Clearing your router's ARP entry for your QNX device will bring it back online. Alternativly, if you don't want to log into your router and clear arp entries you can put your QNX devices on a dedicated VLAN/Sub-interface and set a low ARP timeout for that sub-interface. After the ARP entry for the QNX device times out, the router will broadcast an ARP request, the QNX device will reply, and all will start working again.
The reason I suggest a dedicated sub-interface is just to keep the ARP broadcast chatter down. But if you don't have a lot of devices on your L2 network, you can just lower the ARP timeout on the router interface.