By default, when you install snmpd (this was tested on Ubuntu 10.04, not sure about other Linux variants), the daemon is set to listen only on 127.0.0.1 (localhost)
If you run chech the process, you can see this:
techedemic@demo:/etc/default$ ps awux | grep snmp snmp 32753 0.3 2.0 47916 4948 ? S 09:29 0:00 /usr/sbin/snmpd -Lsd -Lf /dev/null -u snmp -g snmp -I -smux -p /var/run/snmpd.pid 127.0.0.1 sintrex 32757 0.0 0.3 7624 904 pts/0 S+ 09:29 0:00 grep --color=auto snmp |
To allow access to any machine from outside (make sure your company security policies allow for this), you need to edit the /etc/default/snmpd file as follows: