Windows NAT router

Hi,

I have Configured a Windows 2003 Server as a NAT Router.
Following is my COnfiguration:

1. 2 Networks (Public 15.154.59.0 & Private 192.168.1.0)
2. Configured Windows server with 2 NIC (Network COnnections , public IP-15.154.59.232 & Private IP – 192.168.1.1) as NAT Router.
3. When I try to ping the machine in 15.154.59.0 network from the machine in Private network 192.168.1.2 , I am unable to do it. It says “Destination Host Unreachable”

Can anyone suggest why is this happening this way?

Thanks in Advance,
Vasavi