If are seeing a lots of “TCP: drop open request from A.B.C.D” messages and you don’t expect a real load the server, you’ll need to enable syncookies. Edit your /etc/sysctl.conf and append the following lines:
# enable syncookies net.ipv4.tcp_syncookies = 1
Then restart network service.
[root@centurion ~]# /etc/init.d/network restart Shutting down interface eth0: [ OK ] Shutting down loopback interface: [ OK ] Setting network parameters: [ OK ] Bringing up loopback interface: [ OK ] Bringing up interface eth0: [ OK ]