[This is preliminary documentation and subject to change.]
Further description:
The subnet associated with the IP transport address specified in the AgentAddress qualifier of the SNMP device namespace instance or SNMP-compatible class is known by a local router. However, the IP transport address on that subnet is not discoverable by the subnet connected router using the address resolution protocol.
Solution:
Verify that the IP address is correct and that the hardware device is switched on and connected to the network.