Add a custom "X-forwarded-for" header name

Nandhi You should be able to do this with an HTTP profile with XFF enabled and it should let you name it what you wish rather than using an iRule.

Hi Nandhi, I am not able to get the profile suggestions by Paulius or zamroni777 working in my local lab (happy to be told what I'm doing wrong!) but I am able to a) remove any existing X-Forwarded-For that arrives and b) insert new based on the requests client IP address both via iRule and local traffic policy. I find the traffic policy overly complicated as it requires Tcl anyway, so personally I'd use the iRule, but both solutions work.

iRule

when HTTP_REQUEST {
    if { [HTTP::header exists "X-Forwarded-For"] } {
        HTTP::header remove "X-Forwarded-For"
    }
    HTTP::header insert "X-Custom-XFF" [IP::client_addr]
}

Policy

ltm policy insert_custom_xff {
    last-modified 2024-01-10:15:50:09
    requires { http }
    rules {
        custom_xff {
            actions {
                0 {
                    http-header
                    insert
                    name X-Custom-XFF
                    value tcl:[IP::client_addr]
                }
            }
            ordinal 1
        }
        remove_std_xff {
            actions {
                0 {
                    http-header
                    remove
                    name X-Forwarded-For
                }
            }
        }
    }
    status published
    strategy all-match
}

it's better to use gui based local traffic policy rather than irules to avoid scripting typo

https://community.f5.com/t5/technical-articles/to-irule-or-not-to-irule-introduction-to-local-traffic-policies/ta-p/279536

Thanks Paulius & Zamroni.

The actual need is bit different. The end point expecting the header name "HTTP_XFF" with original client IP. By default, header name uses the string X-forwarded-for:<client-ip>

The end point does not support "X-forwarded-for" and supported configuration is ,<add key="LoadBalancerClientAddressHeader" Value="HTTP_XFF"/>

In your first post you wrote client side, but your iRule manipulates the header that will be sent to the server side.