root@server107 [~]# apf -r
Development mode enabled!; firewall will flush every 5 minutes.
iptables v1.2.9: host/network `at' not found
Try `iptables -h' or 'iptables --help' for more information.
iptables v1.2.9: host/network `at' not found
Try `iptables -h' or 'iptables --help' for more information.

Why am I getting the error:
iptables v1.2.9: host/network `at' not found