[syslog-ng]pings from loghost

Dear list, I have set up a loghost using syslog-ng 1.4.14 on an AIX-Box. Now there is the phenomenon that the loghost tries to send ICMP echo requests (= pings) to machines from which it is receiving logs. Those pings are blocked by a firewall which is located between the loghost and the other computers. How can I stop the syslog-ng-machine from sending these pings? They are obviously not necessary for the proper work of syslog-ng as the loghost works very well even when the pings are blocked. Thanks in advance, regards, Christian