If your base station or Time Capsule is connected to a router or other network device that’s using Network Address Translation (NAT) to share a single Internet connection with multiple computers on your network, and you are using Dynamic Host Configuration Protocol (DHCP) to provide private IP addresses, you need to turn off NAT and DHCP on the base station or Time Capsule.
Most networks need only one device using NAT and DHCP to provide IP addresses.
Open AirPort Utility, located in the Utilities folder in the Applications folder on a computer using Mac OS X, and in Start > All Programs > AirPort on a Windows computer.
Select the device you’re setting up, and then click Manual Setup. Enter the password if necessary.
Click Internet in the toolbar, and then click Internet Connection.
Choose Off (Bridge Mode) from the Connection Sharing pop-up menu.
With NAT and DHCP turned off, the device acts as a simple bridge between the wired and wireless computers on the network.