if you need the CSS to nat the servers ip addresses when they go out to the Internet, all you need is a group.
ie:
service server1
ip 10.x.x.x
active
servoce server2
ip 10.x.x.x
active
group natservers
vip address x.x.x.x
add service server1
add service server2
active
!
If you already had a group using these services, you will need something a little more tricky.
Just start with the above and let us know if it works.
Gilles.
