Posted by brunov I have the following aflex that will allow you to filter the DNS requests by hostname, and limit what will be load balanced to your DNS servers. Code: when CLIENT_DATA { #capture the udp payload and capture the requested hostname set udplength [UDP::payload length] set udplength [expr "$udplength-13-5"] set dnspayload [UDP::payload 13 $udplength] #replace cntrl character with period and make the hostname human readable regsub -all {[[:cntrl:]]+} $dnspayload {.} payload_sub #compare hostname in request to required hostname list if { ([string first "slb.yahoo.com" $payload_sub] >= 0) or ([string first "slb.google.com" $payload_sub] >= 0) } { pool DNS log "There is a match the request is $payload_sub" } else { reject } } This will allow any request that ends in slb.yahoo.com, or slb.google.com. All other requests will be rejected at the load balancer. Bruno