iRule help request

If you are always triggering off of the second part of the virtual and the mapping is always to apache1."field 2".ee.com, then you can use getfield to extract that value and then dynamically build the pool name

when HTTP_REQUEST { 
   set token [getfield [HTTP::host] "." 2] 
   pool "apache1.$token.ee.com" 
 }

You might want to throw in some error validation to make sure that your generated pool name exists. If it does not, then the iRule will terminate and the connection will be broke.

when HTTP_REQUEST { 
   set token [getfield [HTTP::host] "." 2] 
   if { [catch { pool "apache1.$token.ee.com" } ] } { 
     log local0. "Error using pool apache1.$token.ee.com" 
   } else { 
      do some error handling in here. 
   } 
 }

If there isn't a one-to-one mapping, then you'll likely need to go with the findclass/matchclass option of building a lookup table.

Hope this helps...

-Joe