[LARTC] multiple routing tables for internal router programs

[Andrea]

Maybe a strange request, I'll try to explain this as clearer as I can 
(forgive my bad english, please  :-)  ).

I'm setting a linux box as a router. My router uses multiple routing 
tables, so I can address the traffic from specific ip addresses of my 
lan to distinct ISPs providers (specifying a different default gateway 
fo r each table), marking packets with iptables (prerouting marks).

This works with the forwarding traffic (lan-ISPs) that crosses my router.

But how can I reach the same result for programs/services that are 
working INTO the linux box? All I want is that a program (ping, for 
examples, or a VOIP server, better) uses a secondary routing table in 
the same machine. In this mode, I can manipulate route settings for 
different classes of program in my router.

Is it possible?

Thanks