Internet Connection Sharing DHCP

I'm trying to set up internet connection sharing on my Macbook Pro in order to connect an ipad to an office network.

I have created a network using the airport on the Macbook, and then used internet connection sharing to share the ethernet connection of the Macbook over the airport. I can connect the ipad to the Macbook, and it gets on the internet just fine.

What I really want to do is connect to a computer on my internal network using an app on the ipad. The problem is, the IP address that is given to the ipad is not on my internal network. I'm trying to figure out where the DHCP server is that the ipad gets an IP address from.

My internal network is in the 192.168.1.xxx range. I have a DHCP server enabled in my router that gives out addresses between 192.168.1.200 and 192.169.1.254. All addresses below 1922.168.1.200 are set manually (the computer I wish to connect my ipad to is at 192.168.1.19).

When I look at the ipad settings, it tells me the IP address it has been given is 10.0.2.2, with a router of 10.0.2.1. I can't figure out where it got this address. My assumption is that this address came from the Macbook which is somehow acting as a DHCP server and NAT router to share the internet connection. But I can't find any settings anywhere on the Macbook that would allow me to configure this.

So, my question is whether I can somehow manipulate what the addresses the Macbook doles out. My understanding of routing is a bit sparse, but I'm wondering if there is a simple way to have the ipad connect to my internal network.

Thanks.

steve