Libnet Sending Problems

Hello everyone
 
I have written a program using libpcap and libnet and when i went to test the main functionality i noticed some problems.
 
The problem i am having is this,
    
        Lets say i have 3 machines, 2 on the same domain, and 1 on a seperate domain,  the problem i am having is when i call the libnet write and try to send from one domain to another domain the packet never reaches the other computer, however when i call libnet write and send to the other machine in my SAME domain the packet gets there fine,  Does libnet not support sending to machines on different domains,  there is a route from the domains, i am able to ping to the machines on the seperate domains
 
Thank you for any help
jason