Some Hardware Load-balancers such Cisco's CSS and BigIP Products test the readiness of the backend Machines with SYN-ACK-RST.
This behavior causes a 400 error in nginx.
With the GEO Module and the if-Statement you can omit these entries:
http {
geo $lb {
default 0;
10.1.1.1/32 1; # LB IPs
10.1.1.2/32 1;
}
# ...
server {
# ...
access_log /path/to/log;
error_page 400 /400;
location = /400 {
if ($lb) {
access_log off;
}
return 400;
}
}
}