Linksys AG241 Planning Your Network, Gateway’s Functions, IP Addresses, What’s an IP Address?

ADSL2 Gateway with 4-Port Switch

Chapter 2: Planning Your Network

The Gateway’s Functions

A Gateway is a network device that connects two networks together.

In this instance, the Gateway connects your Local Area Network (LAN), or the group of computers in your home or office, to the Internet. The Gateway processes and regulates the data that travels between these two networks.

The Gateway’s NAT feature protects your network of computers so users on the public, Internet side cannot “see” your computers. This is how your network remains private. The Gateway protects your network by inspecting every packet coming in through the Internet port before delivery to the appropriate computer on your network. The Gateway inspects Internet port services like the web server, ftp server, or other Internet applications, and, if allowed, it will forward the packet to the appropriate computer on the LAN side.

Remember that the Gateway’s ports connect to two sides. The LAN ports connect to the LAN, and the ADSL port connects to the Internet. The LAN ports transmit data at 10/100Mbps.

IP Addresses

What’s an IP Address?

IP stands for Internet Protocol. Every device on an IP-based network, including computers, print servers, and Gateways, requires an IP address to identify its “location,” or address, on the network. This applies to both the Internet and LAN connections. There are two ways of assigning an IP address to your network devices. You can assign static IP addresses or use the Gateway to assign IP addresses dynamically.

Static IP Addresses

A static IP address is a fixed IP address that you assign manually to a computer or other device on the network. Since a static IP address remains valid until you disable it, static IP addressing ensures that the device assigned it will always have that same IP address until you change it. Static IP addresses must be unique and are commonly used with network devices such as server computers or print servers.

Chapter 2: Planning Your Network

Figure 2-1: Network

LAN: the computers and networking products that make up your local network

NOTE: Since the Gateway is a device that connects two networks, it needs two IP addresses—one for the LAN, and one for the Internet. In this User Guide, you’ll see references to the “Internet IP address” and the “LAN IP address.”

Since the Gateway uses NAT technology, the only IP address that can be seen from the Internet for your network is the Gateway’s Internet IP address. However, even this Internet IP address can be blocked, so that the Gateway and network seem invisible to the Internet— see the Block WAN Requests description under Security in “Chapter 5: Configuring the Gateway.”

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The Gateway’s Functions