LTM for load balance DNS queries with real IP addresses

make dns server's routing config to clients goes thorugh f5, e.g using pbr in intermediate router, make f5 floating ip as default gw or etc.
hence you dont need to enable snat in f5 vserver config and dns servers can see clients ip addres.

if you want f5 gtm/dns at low price, you can try the virtual edition.
dns traffic is low because clients only do 1 dns request for many application requests.