By default, (on RHEL/CentOS, at least) snmpd will log all connection attempts, which can turn your /var/log/messages into a giant mess, looking something like this…

Sep  8 10:26:00 deathstar snmpd[25387]: Connection from UDP: [192.168.12.32]:35794->[192.168.23.54]
Sep  8 10:26:00 deathstar snmpd[25387]: Connection from UDP: [192.168.12.32]:35794->[192.168.23.54]
Sep  8 10:26:00 deathstar snmpd[25387]: Connection from UDP: [192.168.12.32]:35794->[192.168.23.54]
Sep  8 10:26:00 deathstar snmpd[25387]: Connection from UDP: [192.168.12.32]:35794->[192.168.23.54]
Sep  8 10:26:00 deathstar snmpd[25387]: Connection from UDP: [192.168.12.32]:35794->[192.168.23.54]

The entries are repetitive and, in most cases, are of no value. They simply tell you that some server out there has tried to connect to the SNMP service. With a large number of incoming connections, much of your server’s resources may be wasted on logging this useless data.

Since the net-snmp v 5.3, you have the ability to disable this particular log message. Below if a quick overview tested on RHEL 6.3.

Update net-snmp:

yum -y update net-snmp

Update /etc/snmp/snmpd.conf

cat << EOF >> /etc/snmp/snmpd.conf
dontLogTCPWrappersConnects 1
EOF

Update /etc/sysconfig/snmpd (see note below)

cat << EOF >> /etc/sysconfig/snmpd
OPTIONS="-Lsd -Lf /dev/null -p /var/run/snmpd.pid"
EOF

Restart snmpd

/sbin/service snmpd restart

Note: you may need to edit either /etc/sysconfig/snmpd or /etc/sysconfig/snmpd.options. Check /etc/init.d/snmpd for the following “if” statement to figure out which file to edit (or create):

if [ -e /etc/sysconfig/snmpd ]; then
  . /etc/sysconfig/snmpd
fi