Access from other domains

My pressbooks site works well.

It is located on address.dom2.dom1.com

All machines on dom2.dom1.com can see it just fine.

But machines on dom1.com are not able to see it. They cannot access it even when typing the ip address of the site.

I am kinda stumped on this one. Firewall is off. Site ip can be pinged from anywhere.

Would anybody have any suggestions ?

Thanks