Airport extreme wireless network

My Apple MD0031B/A Airport Extreme Wireless N Gigabit Cable Router, would not allow me to change the router mode, but it turned out that I should have attempted to create a wireless network, instead of extending a wireless network.

After getting past the setting up of the Airport Extreme I enabled the Guest network hoping to use the same WPA2 Personal encryption key I used to setup the created wireless network and then connect my Apple TV to it, but I could not do that because the Guest account needs to use DHCP & NAT Protocol (off bridge mode) does not offer that, so I am using the Airport extreme main wireless network with the last few mac address digits as ID

In summary I tried to set up the Airport Extreme using DHCP & NAT and this is where my trouble starts.

My original configuration is a Modem and Router setup The ADSL Modem takes the BT Line in and I pass that to my Router which connects all my machines to the internet, basically the router does all the heavy lifting. Modem = LINKSYS ADSL2 Modem ( 1 Ethernet port ) Router = BUFFALO Air Station Wireless G, DD-WRT v24 (08/15/07) Buffalo-EU (SVN revision 7672) – which now has the Airport Extreme connected.

My Buffalo router has an IP Range of 192.168.11.100 – 149

The Buffalo gateway IP Address is 192.168.11.1

When I try to setup DHCP & NAT within the Airport Extreme I get a DHCP Range conflict ? this is where I have ended up not understanding what the solution is to this.

The Airport extreme reports an IP Address of 192.168.11.115 that also corresponds with the LAN Cable port connection – I have actually seen 192.168.11.147 on my Buffalo router, incidentally that IP corresponds to the mac address of the 2.4Ghz wireless part of the Airport Extreme.

I just need to know what range I should be selecting to make the DHCP & NAT work on the Airport Extreme which should then enable me to use the Guest network, which will allow me to place the Apple TV within that network.

Finally I have 3 x Win 7 machines that all have iTunes home sharing enabled – the Apple TV controlled them previously via the Buffalo router but now that I use the Apple TV through the Airport extreme Wi-Fi the only Home share machine I see is the macbook, and not any of the 3 x win7 machines – does anybody know how I can see those machines through the current Apple TV set up ?

Currently I have the macbook mavericks OSX 10.9.5 and the Apple TV working via through the Airport extremes wireless network

Thanks for looking