when you ping real server, the CSS just forwards the fragment.
When you ping the vip, the CSS would need to reassemble the packet before responding and this is what is not supported.
Regarding stree test, using ping has always been a bad method [whatever the product you want to test].
You should use real traffic.
If your CSS is being used to loadbalance HTTP traffic, then you should send HTTP traffic.
Spirent provides very good testing products.
Otherwise a Perl script usually can do the trick if you can program.
Regards,
Gilles.
