Apparently Net-SNMP is now included in Solaris 10 by default, however it is not enabled by default. To use it you must first disable Sun’s SNMP.

#svcadm disable svc:/application/management/snmpdx:default

Net-SNMP is part of Solaris’ System Management Agent. More about that here:
Solaris System Management Agent Developer’s Guide

Net-SNMP daemon is located at /usr/sfw/sbin/snmpd, and
its configuration file is located in /etc/sma/snmp.

You will need to use svcadm to start and stop Net-SNMP:

#svcadm enable svc:/application/management/sma:default
#svcadm disable svc:/application/management/sma:default

Apparently there are two logs that you can reference for Net-SNMP

SMA’s log is located here — /var/svc/log/application-management-sma\:default.log.
However the default log
file of snmpd is /var/log/snmpd.log.

You also have an init script in /etc/init.d called  init.sma