With IPHost Network Monitor you can run simple snmp requests against a D-Link device in your network.
agentRs232PortConfig
agent Rs232 Port Config
1.3.6.1.4.1.171.12.1.2.4
This object indicates the RS-232C mode once the device has restarted.
Back to AGENT-GENERAL-MIB MIB page.
IPHost Network monitor allows you to monitor agentRs232PortConfig on D-Link device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring D-Link routers right now.