GTM irule for permanent datacenter respond depend on client ip.

I am looking for GTM irule respond datacenter depend on client source ip. Something like below. Pools do not work for me as I need irule for huge list of WIP.

when DNS_REQUEST { 
if { [IP::addr[IP::client_addr]] equals "1.1.1.1/32" } { 
       datacenter DC1 
}
if { [IP::addr[IP::client_addr]] equals "2.2.2.2/32" } { 
       datacenter DC2 
}
}