Server Load Balancer:Obtain client originating IP addresses on backend servers through an Application Load Balancer

Configure an NGINX server

In this example, the CentOS 7.9 operating system and NGINX 1.20.1 are used. Adjust the configurations based on the environment that you use.

1. Run the command nginx -V | grep http_realip_module on the NGINX server to check whether the http_realip_module module is installed on the NGINX server. NGINX servers use the http_realip_module module to parse the value of X-Forwarded-For.

   If --with-http_realip_module is included in the output, it indicates that http_realip_module is installed on the NGINX server and you can proceed to the next step.

   Sample output which shows that http_realip_module is installed

   nginx version: nginx/1.20.1
   built by gcc 4.8.5 20150623 (Red Hat 4.8.5-44) (GCC) 
   built with OpenSSL 1.1.1k  FIPS 25 Mar 2021
   TLS SNI support enabled
   configure arguments: --prefix=/usr/share/nginx --sbin-path=/usr/sbin/nginx --modules-path=/usr/lib64/nginx/modules --conf-path=/etc/nginx/nginx.conf --error-log-path=/var/log/nginx/error.log --http-log-path=/var/log/nginx/access.log --http-client-body-temp-path=/var/lib/nginx/tmp/client_body --http-proxy-temp-path=/var/lib/nginx/tmp/proxy --http-fastcgi-temp-path=/var/lib/nginx/tmp/fastcgi --http-uwsgi-temp-path=/var/lib/nginx/tmp/uwsgi --http-scgi-temp-path=/var/lib/nginx/tmp/scgi --pid-path=/run/nginx.pid --lock-path=/run/lock/subsys/nginx --user=nginx --group=nginx --with-compat --with-debug --with-file-aio --with-google_perftools_module --with-http_addition_module --with-http_auth_request_module --with-http_dav_module --with-http_degradation_module --with-http_flv_module --with-http_gunzip_module --with-http_gzip_static_module --with-http_image_filter_module=dynamic --with-http_mp4_module --with-http_perl_module=dynamic --with-http_random_index_module --with-http_realip_module --with-http_secure_link_module --with-http_slice_module --with-http_ssl_module --with-http_stub_status_module --with-http_sub_module --with-http_v2_module --with-http_xslt_module=dynamic --with-mail=dynamic --with-mail_ssl_module --with-pcre --with-pcre-jit --with-stream=dynamic --with-stream_ssl_module --with-stream_ssl_preread_module --with-threads --with-cc-opt='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -m64 -mtune=generic' --with-ld-opt='-Wl,-z,relro -specs=/usr/lib/rpm/redhat/redhat-hardened-ld -Wl,-E'
   

   Note

   • NGINX 1.0.4, which was released in 2011, and later support the http_realip_module module. If your NGINX version is earlier than 1.0.4, we recommend that you back up data and upgrade to a later version.

   • If the http_realip_module module is not installed on the NGINX server, compile and install NGINX again, and then install http_realip_module. We recommend that you use package managers such as YUM to install and manage NGINX. Packet managers simplify the process.

2. Modify and save the NGINX configuration file. The following code block shows an example. Run the nginx -t command to query the path of the configuration file, which is /etc/nginx/nginx.conf by default. The path may vary based on the environment that you use.

   http {
     # Set the variable $http_x_forwarded_for, which is used to record the value of X-Forwarded-For.
     log_format  main  '$remote_addr- $remote_user [$time_local] "$request" '
                         '$status $body_bytes_sent "$http_referer" '
                         '"$http_user_agent" "$http_x_forwarded_for"';
     
     # ...
   }
   

3. Run the sudo nginx -s reload command to reload the NGINX configuration file.

Configure an Apache server

In this example, the CentOS 7.9 operating system and Apache 2.4.6 are used. Adjust the configurations based on the environment that you use.

1. Run the command httpd -M | grep remoteip_module on the Apache server to check whether the remoteip_module module is installed on the Apache server. Apache uses remoteip_module to parse the value of X-Forwarded-For.

   If remoteip_module (shared) is included in the output, it indicates that the module is installed on the Apache server and you can proceed to the next step.

   Note

   • Apache 2.4.0, which was released in 2012, and later support the remoteip_module module. If your Apache version is earlier than 2.4.0, we recommend that you back up data and upgrade to a later version.

   • If the remoteip_module module is not installed on the Apache server, compile and install Apache again, and then install remoteip_module. We recommend that you use package managers such as YUM to install and manage Apache. Packet managers simplify the process.

2. Modify and save the Apache configuration file. The following code block shows an example. The default path of the configuration file is /etc/httpd/conf/httpd.conf. The path may vary based on the environment that you use.

   # ...
   <IfModule log_config_module>
   	# Add the LogFormat directive %{X-Forwarded-For}i, which is used to record the information about X-Forwarded-For.
     LogFormat "%{X-Forwarded-For}i %h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
     LogFormat "%{X-Forwarded-For}i %h %l %u %t \"%r\" %>s %b" common
   	#...
   </IfModule>
   # ...

3. Run the command sudo systemctl restart httpd to restart Apache.

Configure an IIS server

In this example, the Windows Server 2016 operating system is used. Adjust the configurations based on the environment that you use.

1. Download and decompress the F5XForwardedFor file.

2. Copy the F5XFFHttpModule.dll and F5XFFHttpModule.ini files from the x86\ or x64 directory to a directory on the IIS server. Make sure that the IIS process has read and write permissions on the directory.

3. Open IIS Manager in Server Manager.

4. Select the IIS server and double-click Modules.

   

5. Click Configure Native Modules, and then click Register in the dialog box that appears.

   

6. Add the downloaded .dll file.

   1. Enter a file name, select a path, and then click OK.

   2. The module to be registered is automatically selected. Click OK.

7. Return to the homepage of IIS Manager and double-click Logging. Configure a log format to record the information about X-Forwarded-For.

   1. Click Select Fields.

      

   2. Click Add Field in the lower-left corner, add the following field, and then click OK.

      

   3. Click Apply in the right-side Actions pane.

8. Restart the IIS server and wait until the configurations take effect.

NGINX server

If you use an NGINX server, you can check the NGINX log to determine whether the backend server can retrieve client IP addresses.

The default path of the NGINX log is /var/log/nginx/access.log.

In each log entry, the leftmost IP address in the $http_x_forwarded_for variable is the client IP address.

Apache server

If you use an Apache server, you can check the Apache log to determine whether the backend server can retrieve client IP addresses.

The default path of the Apache log is /var/log/httpd/access_log.

In each log entry, the leftmost IP address in the %{X-Forwarded-For}i variable is the client IP address.

IIS server

If you use an IIS server, you can check the IIS log to determine whether the backend server can retrieve client IP addresses.

You can find the path to the log file in the Logging module.

In each log entry, the leftmost IP address in X-Forwarded-For is the client IP address.