With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
vmpsLastFailClient
vmps Last Fail Client
1.3.6.1.4.1.9.9.53.1.1.2.1.5
The MAC address of the VLAN client whose last configuration request was rejected. This MAC address will be for the VLAN client who was delivered the last configure response that caused the vmpsOutConfigFails object to increment. This value is taken directly from the configure request and is not guaranteed to be correctly identify a client.
Back to CISCO-VMPS-MIB MIB page.
IPHost Network monitor allows you to monitor vmpsLastFailClient on Cisco device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Cisco routers right now.