Exchange 2010 OWA URL Not Working.

Hi,

for testing i have installed Exchange 2010 in hyper v. but the url of OWA (both external & internal) is not working.

with in lan when type this url  - https://192.168.0.71/owa then  i am getting the OWA page (internally) 

but when i type these url 1. https://mail.domain.com/owa     (external)

                                      2. https://ex.doamin.com/owa     (internal)

it give me an error that the page cannot displayed.

so please help me on this

thanks

Manoj Rana