Redirecting traffic from a non-existent IP

[Julian Hagenauer <chaosbringer@gmx.de>]

Hi,
i am running Linux 2.6.11.12-xen0 (binary distribution).
I want to route all Traffic destined to 192.168.1.5 to 192.168.1.3.
192.168.1.5 is a non-existent IP/host, 192.168.1.3 is a Xen-VM running 
on localhost, so 192.168.1.5 should act as a kind of alias for 
192.168.1.3 and be accessible from localhost.
The following modules are loaded:

Module                  Size  Used by
iptable_filter          2432  0 
iptable_nat            19932  1 
ip_conntrack           38712  1 iptable_nat
ip_tables              20352  2 iptable_filter,iptable_nat
intel_agp              20124  1 
agpgart                28968  1 intel_agp


I wrote and ran the following script on localhost:

#!/bin/bash
echo 1 > /proc/sys/net/ipv4/ip_forward
MAP_FROM=192.168.1.5 # virtuelle IP
MAP_TO=192.168.1.3 # IP einer VM
iptables -t nat -F
echo "Mappe $MAP_FROM nach $MAP_TO..."
iptables -t nat -A PREROUTING -d $MAP_FROM -j DNAT --to $MAP_TO
echo "Aktuelle Nat-Regeln:"
iptables -t nat -L

But ping 192.168.1.5 or ssh 192.168.1.5 still does not work.
I have no clue what's wrong.

Sincerely,
Julian