Sorry. The command is case sensitive. So you'll want to run..
rpm -qa | grep snmp
It should output something similar to the following..
[root@lab-redhat6-app ~]# rpm -qa | grep snmp net-snmp-5.5-12.el6.x86_64 net-snmp-libs-5.5-12.el6.x86_64
To upgrade NET-SNMP on the Redhat machine, it's probably easiest to use yum. It should satisfy any dependencies that also need updating.
yum install net-snmp-utils