first configure the services like this :
service dns1
ip address x.x.x.x
active
service dns2
ip address x.x.x.x
active
Then configure the content rule
owner mycompany
content dns
vip address x.x.x.x
add service dns1
add service dns2
active
!
Then we need to setup something for the dns answer
group dns
vip address x.x.x.x !!!!! same as for the content rule
add service dns1
add service dns2
portmap disable
!
The portmap disable requires software 5.03(33) or above.
The command is also in 5.01
http://www.cisco.com/en/US/products/hw/contnetw/ps789/prod_release_note09186a00800ba0c6.html