SNMP is not enabled in ESXi by default for the reason that there is not much there to query. please put more input about your issue so that we can find out.
Ramesh,Thanks for the response,configaration from esxi level has been completed to a test trap receiver.I just need to know if I enable snmp on more than 170 esxi hosts ,what will happen to network traffic? will it(monitoring software/server) be able to handle the udp traffic?
I don't see any issue in this. We monitor much more (not only ESXi servers) but around 300 Linux systems on a monitoring server running PRTG Network Monitor. Works like a charm.