Configure each managed ESX server to enable SNMP polling and allow discovery and monitoring by the Server Manager and IP Manager. You need to discover the ESX through SNMP in order to build the link between the physical interfaces and the physical switches. MIB2 and HostResources MIB are required for proper discovery and monitoring.
VMware documentation provides information on how to set up SNMP for specific versions of VMware ESX servers.
By default ESM uses VirtualCenter to discover and monitor ESX servers. In addition, ESM relies on IP Domain Managers to discover physical interfaces on ESX servers. This data is vital for creating complete virtual networking topology, and create a link between Virtual and Physical networks.
To create connections between a virtual switch (Standard vSwitch, Distributed vSwitch and Nexus 1000 vSwitch) and an ESX server, the Cisco Discovery Protocol must be enabled on both the physical switch and the virtual switch.
The CDP must be running in both Listen and Advertize mode. “Enabling Cisco Discovery Protocol (CDP)” on page 85 provides instructions.