With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
cagwDhcpDeclinePackets
Cisco's ASN Gateway Dhcp Decline Packets
1.3.6.1.4.1.9.9.638.1.3.2.1.1.4
The number of DHCP Decline packets transmitted by the DHCP relay in the ASN-GW to the DHCP server.
Back to CISCO-ASN-GATEWAY-MIB MIB page.
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