Access WAS externally via NAT ?

Dear colleagues,

we try to access a WAS 6.20 from the internet through a firewall. Our WAS is located in the DMZ and has got a private IP address. The request from the internet is redirectet from the firewall to the http-port of the WAS. At connecting from the internet a message is shown in the browser which says: side can not be shown.

If we try to reach the WAS inside the LAN everything is fine - what do we have to do to access the WAS externally via NAT ?

Regards

Michael