If you configure the ESXi embedded SNMP agent for polling, it can listen for and respond to requests such as GET requests from SNMP management client systems.
By default, the embedded SNMP agent listens on UDP port 161 for polling requests from management systems. You can use the vicfg-snmp command to configure an alternative port. To avoid conflicts with other services, use a UDP port that is not defined in /etc/services.
Important: Both the embedded SNMP agent and the Net-SNMP-based agent available in the ESX 4.x service console listen on UDP port 161 by default. If you are using an ESX 4.x system, change the port for one agent to enable both agents for polling.