Windows Media encoder 9 IP Problem ?

I always get ip http://192.168.1.100 which is virtual not real
when i put in the code no one can listen to the broad cast except me
but some times i get real ip 41.xx.xx.xx
then the broadcast woks well

can any body tell me how to make wme recognize this real ip all the time?

 

or how to port forward this application?

 

and what is DMZ enabling
and how to enable this

plz help