HWLoadbalancerCheckErrors

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;
    }
  }
}