### 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](# "NginxHttpGeoModule") 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; } } } ~~~