Could you please let us know little bit more information about this router in particular? For example:
- Was router working before and suddenly just stopped? If it happen recently, maybe you remember what have been done with the router, e.g. maybe you were changing router's configuration prior to this issue occurring?
- Is only single LAN port on the router not working, or are all 3 LAN ports not working simultaneously?
- Could you please try to use different LAN cable, just to be sure that issue is not related with damaged cable?
- Does this RUT500 keep broadcasting its WiFi SSID? Is device reachable via WiFi?