RHEL 6.3 SNMP Test failed

Hi, I have several RHEL 6.3 VMs running on Vsphere 5.1. When I try to add a node using SNMP, I get 'Test Failed' error. All my other Windows VMs are working fine.

I have edited snmpd.conf numerous times and still it doesn''t work. UDP/TCP 161 is open. What could be the problem here?

Any help is greatly appreciated.