SNMP daemon will by default generate a lot of noise in /var/log/messages:

Aug 28 04:08:50 <hostname> snmpd[3664]: Connection from UDP: [<IP>]:1921
Aug 28 04:10:22 <hostname> last message repeated 3 times
Aug 28 04:11:25 <hostname> last message repeated 50 times
Aug 28 04:11:41 <hostname> last message repeated 33 times

Add following into /etc/sysconfig/snmpd.options and restart SNMP daemon to get rid of these messages

echo 'OPTIONS="-LS 5 d -Lf /dev/null -p /var/run/snmpd.pid -a"' >> /etc/sysconfig/snmpd.options
service snmpd restart

http://raetsel.wordpress.com/2008/02/15/snmpd-filling-up-varlogmessages