[ubuntu] Having problems accessing webserver, inside the network, using public domain name. topic

I've got an ubuntu server that's running apache and has Zurmo, which is a crm software. The crm software likes to redirect every page to my public domain name, which is controlled by a dynamic dns server. I have a dhcp server and a dns server active on the network also. What do I have to do, to be able to use my public domain name from within my lan? I want to be able to do this will all of the computers on my lan.

thanks in advance