device status down but able to index interfand can do verbos

[_raindrop18]

I have couple of devices the device status down with snmp up time but Cacti ready system information of the device and index the interface also can do verbos query and able create graph. but the graph is nan and the status down. very starnge for me. how come Cacti can do snmp query and get device info but the status is down?! any idea???