By default net-snmpd logs plenty of information to the /var/log/messages like:
Nov 21 04:02:32 ns snmpd[1960]: Connection from UDP: [12.34.56.78]:1128->[78.56
.34.12] REFUSED
Nov 21 04:02:35 ns last message repeated 5 times
Nov 21 04:03:20 ns snmpd[1960]: Connection from UDP: [23.45.67.89]:1089->[78.56
.34.12] REFUSED
Nov 21 04:03:23 ns last message repeated 5 times
It’s rather annoying. If you’re using CentOS then edit /etc/sysconfig/snmpd and add the following line:
OPTIONS=”-LSwd -Lf /dev/null -p /var/run/snmpd.pid -a”
This says that syslogd should send logging (L) information to syslog (S) into LOG_DAEMON (d) facility for LOG_ERR (e) and all upper priorities.
Don’t forget to restart snmpd service.