iRule to point to two DNS servers depending on domain

Hi all,

So we have a situation where we are using the BIG-IP to act as an RDP gateway to two separate domains.

So basically a single workstation can RDP into two separate domains. We need the F5 to resolve IP addresses to the correct hostname.

Now this works perfectly fine for the first DNS server + domain in our list as configured by System > Configuration > Device > DNS.

However the 2nd domain fails as I don't think the requests reach the 2nd DNS server.

I am wondering if there is an iRule we can create that will route certain destination IP/hostnames to a certain DNS server for resolution.

This is what I tried to create myself but I think I may have been slightly off...

when DNS_REQUEST {
    if { [IP::client_addr] starts_with  "10.10.10." } {
       switch -glob [string tolower [DNS::rrname]] {
    "domain1.com" -
        pool DNS_1
    }
    default {
         pool DNS_2
    }
     }
   } 

So i'm trying to point anything looking for domain1.com to DNS_1 pool and everything else to DNS_2 pool...but I think I may be completely off base!

Are there any iRule wizards that can assist?

Thanks!