Hi,
I don't your LAN setup, I can answer you from the following assumption.
1. You have a LAN with all Private/Local IP address.
2. You have few Public/Global IP address.
3. There is a NAT box between your Network and public/global/internet.
Here the NAT is used to communicate with public network. by default NAT converts and maintenance the private IP to public IP. so if you have a Public IP address in side a private network, i can not communicate to Public Address.
(Because Different N/W , Different Mask, and broadcast IP).
Of course few people put their Public server inside a private network due to some security issue, and proper configure NAT can help to communicate with outside world.
Regards,
Arul