With IPHost Network Monitor you can run simple snmp requests against a D-Link device in your network.
swRadiusAuthClientIdentifier
Switch Radius Authentication Client Identifier
1.3.6.1.4.1.171.12.3.3.1
NAS Identifier
Back to AUTH-MIB MIB page.
IPHost Network monitor allows you to monitor swRadiusAuthClientIdentifier 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 VPN routers right now.