Let me explain my network:
--PIX506E(I have PIX515E on production) outside connected to PUBLIC VLAN
--Pix Inside connected to Switch private VLAN
because of OLD sin we assign 10.10.8.0/255.255.255.0(means only 253 host) to inside interface.
Now I would like to wash the OLD SIN, I like to expand the network. I know following solution is possiable
 change mask on PIX inside interface 255.255.0.0 -- as this is production setup and I need to do lot of changes in ACL/machine level / load balancer level. Downtime also require for this process.
 I came to know from cisco my pix will support virtual interface so I did following on staging setup:
-pix inside IP is 10.10.8.1
-created Virtual interface virt and IP is 10.10.15.2
now my problem is I am not able to ping 10.10.15.2 from my machines.
please give me suggestion or some other idea which will solve my problem