need iRule redirect help

In the header? Or somewhere in the URI? If it's in the URI, something along these lines will probably do the trick:

  
 when HTTP_REQUEST {  
 if {[HTTP::uri] equals {dfinder.xx.com}} {  
 pool pool_dfinder  
 }  
 }  
 }  
 

This rule assumes that 'pool_common' is the default pool assigned to your virtual server. If you're looking in the header for 'dfiner.xx.com', you'd want this:

  
 when HTTP_REQUEST {  
 if { [HTTP::header "Foo"] equals "dfinder.xx.com" }  {   
 pool pool_dfinder  
 }   
 }  
 

...though you'd obviously want to change "Foo" to whatever header contains the value 'dfinder.xx.com'.

There's more on testing headers here:

http://devcentral.f5.com/wiki/default.aspx/iRules/HTTP__header.html