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Notes on Getting Real Client IPs by CLB

All layer-4 (TCP/UDP/TCP SSL) and layer-7 (HTTP/HTTPS) CLB services support getting a real client IP directly on a backend CVM instance with no additional configuration required.

• For layer-4 CLB, the source IP obtained on the backend CVM instance is the client IP.
• For layer-7 CLB, you can use the X-Forwarded-For or remote_addr field to directly get the client IP. For the access logs of layer-7 CLB, see Configuring Access Logs.

Note：

• For layer-4 CLB, the client IP can be directly obtained with no additional configuration required on the backend CVM instance.
• For other layer-7 load balancing services with SNAT enabled, you need to configure the backend CVM instance and then use X-Forwarded-For to get the real client IP.

Below are commonly used application server configuration schemes.

IIS 6 Configuration Scheme

1. Download and install the F5XForwardedFor plugin module, copy F5XForwardedFor.dll in the x86\Release or x64\Release directory based on your server operating system version to a certain directory (such as C:\ISAPIFilters in this document), and make sure that the IIS process has read permission to this directory.
2. Open the IIS Manager, find the currently opened website, right-click the website, and select Properties to open the properties page.
3. On the properties page, switch to ISAPI Filters and click Add to pop up the Add/Edit Filter Properties window.
4. In the Add/Edit Filter Properties window, enter "F5XForwardedFor" for "Filter name" and the full path to F5XForwardedFor.dll for "Executable" and then click OK.
5. Restart the IIS server for the configuration to take effect.

IIS 7 Configuration Scheme

1. Download and install the F5XForwardedFor plugin module, copy F5XFFHttpModule.dll and F5XFFHttpModule.ini in the x86\Release or x64\Release directory based on your server operating system version to a certain directory (such as C:\x_forwarded_for in this document), and make sure that the IIS process has read permission to this directory.
2. Select IIS Server and double-click Modules.
   
3. Click Configure Native Modules.
   
4. In the pop-up window, click Register.
   
5. Add the downloaded DLL files as shown below:
   
6. After adding the files, select them and click OK.
   
7. Add the above two DLL files in "ISAPI and CGI Restrictions" and set the restrictions to "Allow".
   
8. Restart the IIS server for the configuration to take effect.

Apache Configuration Scheme

1. Install the third-party Apache module "mod_rpaf".

   wget http://stderr.net/apache/rpaf/download/mod_rpaf-0.6.tar.gz
   tar zxvf mod_rpaf-0.6.tar.gz
   cd mod_rpaf-0.6
   /usr/bin/apxs -i -c -n mod_rpaf-2.0.so mod_rpaf-2.0.c
   

2. Modify the Apache configuration /etc/httpd/conf/httpd.conf by adding the following to the end of the file:

   LoadModule rpaf_module modules/mod_rpaf-2.0.so
   RPAFenable On
   RPAFsethostname On
   RPAFproxy_ips IP address (this is not the public IP provided by CLB. For the specific IP, query the Apache logs. Generally, there are two IP addresses and you need to enter both of them)
   RPAFheader X-Forwarded-For
   

3. After adding the above content, restart Apache.

   /usr/sbin/apachectl restart
   

Nginx Configuration Scheme

1. You can use http_realip_module to get the real client IP when Nginx is used as the server. However, this module is not installed in Nginx by default, and you need to recompile Nginx to add --with-http_realip_module.

   yum -y install gcc pcre pcre-devel zlib zlib-devel openssl openssl-devel
   wget http://nginx.org/download/nginx-1.17.0.tar.gz
   tar zxvf nginx-1.17.0.tar.gz
   cd nginx-1.17.0
   ./configure --prefix=/path/server/nginx --with-http_stub_status_module --without-http-cache --with-http_ssl_module --with-http_realip_module
   make
   make install
   

2. Modify the nginx.conf file.

   vi /etc/nginx/nginx.conf
   

Modify the configuration fields and information in red as follows:

Note：

Here, you need to change xx.xx.xx.xx to the actual IP address (not the public IP provided by CLB). For the specific IP address, query the previous Nginx logs. You need to enter all IP addresses if there are multiple ones.

  
fastcgi connect_timeout 300;
fastcgi send_timeout 300;
fastcgi read_timeout 300;
fastcgi buffer_size 64k;
fastcgi buffers 4 64k;
fastcgi busy_buffers_size 128k;
fastcgi temp_file_write_size 128k;

set_real_ip_from xx.xx.xx.xx;
real_ip_header X-Forwarded-For;
 

service nginx restart

4. View Nginx access logs to get the real client IP.

   cat /path/server/nginx/logs/access.log