kind of "ntp relay"

Hi!

My old 3640 router (192.168.254.1/24) just died. RIP. I put in its place a 1600 (12.0 ios) wich does not work as ntp server.

As all my computers connect to it to set their time and date, and since I have a second ntp server (192.168.254.13), i thought to do double-nat (source and destination) on ntp port..

Of course, I only have one ethernet interface, and only one net (192.168.254.0/24).

Here is the configuration I made :

interface Loopback0 ip address 192.168.253.1 255.255.255.252 ip nat inside ! interface Ethernet0 ip address 192.168.254.1 255.255.255.0 ip nat outside ip policy route-map Ntp ! ip nat inside source static udp 192.168.254.13 123 192.168.254.1 123 ip nat outside source static udp 192.168.254.1 123 192.168.254.13 123 ! access-list 101 permit udp any eq ntp host 192.168.254.1 eq ntp route-map Ntp permit 10 match ip address 101 set ip next-hop 192.168.253.2

... but it doesn't work. It just do destination nat, then packets don't return to the correct source, and of course, they are dropped. :(

Someone could tell me what I've done bad ?

thank you :)