An element management system enables a network management server to provide a variable value to a management information base of a managed device independent of whether the managed device is served by a network address translation firewall. The element management system comprises an SNMP message manager which receives periodic heart beat frames from the managed device and stored identification of a heart beat channel in association with identification of the managed device in a registration table. The heart beat channel comprises the source socket and destination socket of the heart beat frame. The SNMP message manager further uniquely associates an assigned UDP port number with the managed device and provides the unique association of the assigned UDP port and the managed device to the network management server. The SNMP message manager further receives an SNMP Set from the network management server embodied as an IP frame addressed to the assigned UDP port number, looks up the managed device associated with the assigned UDP port number, and sends the SNMP Set to the managed device using the heartbeat channel.