Address Data Group with switch option in iRule.

Best way may be like this...

when DNS_REQUEST {
     Get the status
    switch [IP::remote_addr] {   
        "10.10.10.0/24" -
        "10.10.20.0/24" -
        "10.10.30.0/24" {
            set status [LB::status vs Client1]
        }
        "10.20.10.0/24" -
        "10.20.20.0/24" -
        "10.20.30.0/24" {
            set status [LB::status vs Client2]

        } 
    }

     Handle the status
    if {$status equals "up"} {
        host 1.1.1.1
    } else {
        host 2.2.2.2
    }    
}