NAS (Network Attached Storage) devices are increasing in popularity as more households have their own local networks installed with multiple computers connected. Having an NAS device on the network makes accomplishing tasks such as file sharing and backing up data to a central location much easier and more convenient. External hard drives can function as NAS devices if they are connected to a host that supports networking, such as a home router with a USB port connection.
Install a home router with a USB port. This router can be wired or wireless and does not necessarily have to serve as the main router on the local network.
Enter the router's configuration page. This is normally accomplished by opening a Web browser and entering the IP address "192.168.1.1" or "192.168.0.1" without quotes.
Click on the "Storage" link to configure the external hard drive. The options include formatting the disk and creating new shares.
Connect to the configured shares over the network. For example, if the router has the network name "ROUTER" the client computer can connect to the external hard drive, now functioning as a NAS, by entering "\ROUTER\share-name" without quotes.
Many newer home routers (both wired and wireless) support USB devices, such as external hard drives.