Cisco Systems WRVS4400NRF manual Networking and Security Basics

Networking and Security Basics	2
The Use of IP Addresses

If you use the router to share your cable or DSL Internet connection, contact your ISP to find out if they have assigned a static IP address to your account. If so, you will need that static IP address when configuring the router. You can get the information from your ISP.

A dynamic IP address is automatically assigned to a device on the network. These IP addresses are called dynamic because they are only temporarily assigned to the personal computer or other device. After a certain time period, they expire and may change. If a personal computer logs onto the network (or the Internet) and its dynamic IP address has expired, the DHCP server will assign it a new dynamic IP address.

A DHCP server can either be a designated personal computer on the network or another network device, such as the router. By default, the router’s Internet Connection Type is Obtain an IP automatically (DHCP).

The personal computer or network device obtaining an IP address is called the DHCP client. DHCP frees you from having to assign IP addresses manually every time a new user is added to your network.

For DSL users, many ISPs may require you to log on with a user name and password to gain access to the Internet. This is a dedicated, high-speed connection type called Point to Point Protocol over Ethernet (PPPoE). PPPoE is similar to a dial-up connection, but PPPoE does not dial a phone number when establishing a connection. It also will provide the router with a dynamic IP address to establish a connection to the Internet.

By default, a DHCP server (on the LAN side) is enabled on the router. If you already have a DHCP server running on your network, you MUST disable one of the two DHCP servers. If you run more than one DHCP server on your network, you will experience network errors, such as conflicting IP addresses. To disable DHCP on the router, see Configuring Local Area Network (LAN) Settings, page 52

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

Since the router uses NAT technology, the only IP address that can be seen from the Internet for your network is the router’s Internet IP address. However, even this Internet IP address can be blocked so the router and network seem invisible to the Internet.

Cisco WRVS4400N Wireless-N Gigabit Security Router with VPN Administration Guide 10