あ、大丈夫かw

こんな感じ？

interface FastEthernet0/0
ip nat inside
ip policy route-map def-route

interface Dialer0
ip nat outside

interface Dialer1
ip nat outside

route-map def-route permit 10
match ip address 1
set interface Dialer0

route-map def-route permit 20
match ip adress 2
set interface Dialer1

ip nat inside source list 1 interface Dialer0 overload
ip nat inside source list 2 interface Dialer1 overload

access-list 1 permit 192.168.0.0 0.0.0.255
access-list 2 permit 192.168.1.0 0.0.0.255