By Oo Gin Lee

THE cheapest way to set up a home surveillance camera is to do it yourself.

You can get an Internet camera for about $200 which you can then connect to a wired or wireless network at home - just as you would a printer, game console or second PC.

These Net cameras can be connected via a LAN cable to a router or via Wi-Fi.

Most cameras come with cam-control software that can link as many as a dozen cameras in different parts of your home and lets you view them all at the same time on a single screen.

The challenge, however, is when you try to view the live video feeds of the camera on a laptop or even a mobile phone over the Internet.

To understand the challenges, you need to know some networking fundamentals.

Just as every home has a physical address, every digital device - whether it is a router, PC, Net-cam or mobile phone - has a virtual location called an Internet Protocol (IP) address.

Devices need these IP addresses so that they can talk to each other. To connect to your Net camera at home, you must key its IP address into the Web browser of a remote PC or a cellphone and then link up to the camera over the Internet.

The problem, however, is that unlike physical addresses, the IP addresses of devices change over time. This is called dynamicIP.

Such IP addresses are not pre-set into the hardware but assigned by networking equipment when devices such as a surveillance camera connect to the home network or to the Internet.

Today, Internet service providers (ISPs) use dynamic IPs instead of static or fixed IPs because it is more cost-effective to share a pool of IP addresses among its broadband subscribers. (The assumption is that not every subscriber will log on to the Net at the same time.)

For the consumer, though, a dynamic IP address means you can never pinpoint the location of your home PC.

It gets more complicated when you buy a router to set up a network at home so that the multiple devices - PC, Xbox console, camera, iPhone - can share a single Net connection as well as exchange data with each other.

Your router adopts the "external" IP address assigned by the ISP and, in turn, assigns different "internal" IP addresses to each of these devices.

So to get to your camera over the Net, you now have to figure out your router's external IP address followed by the internal IP address of your camera (which is also dynamic).

ISPs discourage home users from setting up their own home servers so many block Web traffic going out from your home network to the Internet.

Unfortunately, this also means your camera cannot send you its video feeds.

Every brand of router and camera has a different control panel, which is why you need to understand these principles and apply them to your individual devices.

Here are some of the challenges I faced with a D-Link DIR685 router and DCS-2121 cam and the solutions to overcome them.

ginlee@sph.com.sg