# Set FastCGI param if exists header

**URL:** <https://www.ruby-forum.com/t/set-fastcgi-param-if-exists-header/219830>\
**Category:** NGINX\
**Created:** [May 17, 2012, 5:34pm UTC](https://www.ruby-forum.com/t/set-fastcgi-param-if-exists-header/219830 "2012-05-17T17:34:09Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Gurdipe\_D](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/b77776/32.png) [@Gurdipe\_D](https://www.ruby-forum.com/u/Gurdipe_D)\
**Post date:** [May 17, 2012, 5:34pm UTC](https://www.ruby-forum.com/t/set-fastcgi-param-if-exists-header/219830/1 "2012-05-17T17:34:09Z")

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Hi guys.

I have a one frontend server with nginx, and 5 backends with PHP-FPM, I  
do  
a FastCGI pass and all works.

Now, I need add other fronted, balanced by hardware base balancer.

My problem is, i need track the remote IP address, is very very  
important,  
in the fastcgi\_params file, actualu REMOTE\_ADDR param is set as  
$remote\_addr.

The balancer sendme a header called x\_cluster\_client\_ip (yes, is ungly),  
i  
recive this in nginx as $http\_x\_cluster\_client\_ip, but if I replace this  
param and reload/restart nginx, before DNS change at the new balancer, i  
don’t get the x\_cluster\_client\_ip value and i don’t can’t know the ip.

there is some form of define REMOTE\_ADDR as $http\_x\_cluster\_client\_ip if  
exists and $remote\_addr else?

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**Author:** ![Tio\_O](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/b9bd4f/32.png) [@Tio\_O](https://www.ruby-forum.com/u/Tio_O)\
**Post date:** [May 17, 2012, 7:32pm UTC](https://www.ruby-forum.com/t/set-fastcgi-param-if-exists-header/219830/2 "2012-05-17T19:32:20Z")

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Today May 17, 2012 at 12:33 Tio O. wrote:

> there is some form of define REMOTE\_ADDR as $http\_x\_cluster\_client\_ip if  
> exists and $remote\_addr else?

You can use realip module:  
[Module ngx\_http\_realip\_module](http://nginx.org/en/docs/http/ngx_http_realip_module.html)

–  
WNGS-RIPE