iRule to change host headers.

  
 when RULE_INIT { 
  
     Set the hostname that the client makes request to (do not include protocol)  
    set ::external_hostname "www.mycompany.co.uk"  
  
     Set the hostname that the BIG-IP will rewrite requests to  
    set ::internal_hostname "www.provider.com"  
  
     Redirect / requests to this URI  
    set ::root_redirect_uri "/aon.asp" 
  
     Log debug messages to /var/log/ltm? 1=yes, 0=no.  
    set ::proxy_site_debug 1  
 }  
 when HTTP_REQUEST { 
  
    if {$::proxy_site_debug}{log local0. "Received request from [IP::client_addr] -> [HTTP::host][HTTP::uri]"}  
  
     Check if request is to root document  
    if {[HTTP::path] eq "/"}{ 
  
       if {$::proxy_site_debug}{log local0. \  
          "Redirecting [IP::client_addr] from / -> https://$::external_hostname$::root_redirect_uri"}  
  
        Redirect to internal hostname and root object  
       HTTP::redirect "https://$::external_hostname$::root_redirect_uri"  
  
    } else {  
  
       if {$::proxy_site_debug}{log local0. "Rewriting [IP::client_addr]'s Host header to $::internal_hostname"}  
  
        We're not redirecting so rewrite the Host header   
       HTTP::header replace "Host" $::internal_hostname  
    }  
 }  
 when HTTP_RESPONSE {  
  
     Check if the status indicates a redirect  
    if {[HTTP::is_redirect]} {  
  
       if {$::proxy_site_debug}{log local0. "Rewriting [IP::client_addr]'s redirect to \  
 [string map -nocase $::internal_hostname $::external_hostname [HTTP::header Location]]"}  
  
        Rewrite the Location header replacing the internal hostname with the external hostname  
       HTTP::header replace Location [string map -nocase $::internal_hostname $::external_hostname [HTTP::header Location]]  
    }  
 }