load balance of DNS server

[Vincent DUQUESNE]

hi,

i have one question for masters !!

i would like to make load balance of DNS servers with CSS (cisco) and i have
a problem.
In fact load balancer don't keep UDP sessions in its sessions tables and
when i would like to make a forward i am not sure that the root server
answer go to the correct DNS server (which make the forward) because the
answer is made on the VIP and is load balanced too !

So my question is : is it possible to change the source port of forward
request or is it possible to force this exchange in TCP mode ?

thanks in advance for your answers

Vincent DUQUESNE