Resolved, ESXi does "not support" the mibs of Dell OMSA (but is able to retrieve the information anyway) I use [URL] (plugin with ESXi compatibility)    
Hello,  I  enable SNMP on esx cli via VSphereClient  vicfg-snmp.pl --server 192.168.3.234 --username root --password @…@ -c publicvicfg-snmp.pl --server 192.168.3.234 --username root --password @...@ -E I set up Dell OpenManage for VMWare ESXi How can I connect dells mibs with the service snmp for ESX? Regards,
OMSA & ESXi