hello mike,
this is tyson, i hope that the answer i gave to your previous query "unable to ping" was helpful.Either you could have disabled arp on that or enabled echo icmp. i lost my previous account so i created a fresh one with an extra one. Any ways let us come to the point ....
If configuring a masquerade address is not possible, you may be able to configure the server to use the IP address of the virtual server by binding the virtual server address to a network interface.
so use: ifconfig [nic]:0 [IP-Address] netmask [mask] up on the back-end ftps server.i,e adding one more ip address to the nic of backend server. But ensure that this new ip would be the "vip ip ".