Many of today’s electronic security systems are designed to operate on a communications/computer network. SDM NetWorkings can help you understand both the intricacies of communication networks, as well as how security systems fit into the networked world. It features excerpts from the “Technician’s Guide to Networking for Security Systems,” a book written by SDM’s contributing technology editor, Dave Engebretson. (See end of article for ordering information.)

One of the basic skills required for technicians to be able to successfully program and install IP network devices is mastery of IP addressing. Every device connected to the network must be properly addressed, or it will not communicate.

Technicians must be capable of checking the IP address of a computer or device, changing the address if needed, and diagnosing address problems.

Let’s review the basics of IP networking:

Each device on a LAN must have a unique IP address, different from all others.

Each IP address must be in the same network as the others on the same LAN, for example, the first three address octets must be exactly the same, with a unique number in the fourth position.

No number in an IP address octet can be higher than 255.

If Wi-Fi and wired Ethernet devices are intermixed on the same network, then each device must have a unique address on the network, for example, a Wi-Fi device cannot have the same IP address as a wired device

When adding a new component, for example a network camera, to an existing network, the technician may need to find or confirm the IP address of a device already connected. This information is needed so that the new device can be addressed to the same Class C network, enabling communication between the devices.

Now, let’s look at some ways to check the IP address of a network-connected device. There is a set of very useful utilities available from the “Command” line in Microsoft Windows. Here’s how to get there.

Click START, then RUN, then type CMD, and click OK.

The command line window will open on your screen. To find the IP address of the computer, type

IPCONFIG and press the “Enter” key.

Here is an example of what you’ll see on the screen.

What does this command tell us about this particular computer? The first line of information shows that this computer is using an Ethernet Wireless connection, so it is communicating with the network via Wi-Fi. The IP address of the listed Wi-Fi adapter is

It is often the case that a computer will have more than one network connection, such as both Wi-Fi and wired Ethernet. Each connection type will have a separate IP address. The IPCONFIG command only tells you the address information of the NICs that are presently enabled on that particular computer.

The “Subnet Mask” of indicates that this computer is connected to a Class C network, which is typical of a LAN within a building or campus of buildings.

The “Default Gateway” is the address of the network router, in this case a Wi-Fi router/switch, with which this particular computer is communicating.

Let’s try a similar exercise that will provide more information about this computer’s IP configuration.

At the command line, type


(Notice that there is a space between the “g” and the “/”)

Here is the information that’s displayed.

The additional information provided by IPCONFIG /ALL includes:

“Host Name” – Computers can have a name, which provides an easy nomenclature for locating a specific computer or files on that computer that are accessible. Here the host name is “David.”

“Node Type” – As this computer has the capabilities of both wired Ethernet and wireless Wi-Fi, it is a “Hybrid.”

Under the “Wireless Network Connection 2” heading, the information provides:

“Description” – make and model of the Wi-Fi card programmed for that particular connection;

“Physical Address” – this is the MAC address of the Wi-Fi card; and

“DHCP Enabled” – this selection indicates whether this particular network interface card will accept IP addresses provided by the system’s router/gateway. In this case DHCP is disabled. This means that the IP address for this NIC must be manually assigned.

While the IP Address, Subnet Mask, and Default Gateway information is the same as with the IPCONFIG command, IPCONFIG /ALL also provides the IP addresses of the DNS (Domain Name Service) servers used by this particular connection to convert alpha-numeric names such as into their numeric IP addresses.

The PING command verifies that communications are available between a node on the network or Internet and a particular laptop or desktop.

At the command prompt, type PING (space) and the IP address or name of a network host, such as a PC name on the network or an Internet URL such as

The PING command sends four data packets to the target IP address or URL, which sends responses back for each packet. PINGing a device verifies that an active network adapter on the PC can communicate with the other node.

After completing the inquiry, exit the command line by typing EXIT and pressing the enter key.

Command line functions can provide many quick and easy tools for checking the status of a computer and its network connections.

Many computer users find that it is easier to utilize a graphic user interface (GUI), pointing and clicking with a mouse, than remembering and typing command line functions. Windows provides the same information as the command line, and we can access the IP information through the Windows GUI.

To check the IP information from Windows XP, click through the following steps: