Deciding when to use a broadband router Chapel Hill NC

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Originally published at Internet.com

Someone posed a technical question to me recently about the need for a broadband router in situations where an Internet connection isn't being shared. The scenario is more common than you might think considering that there are still plenty of people who maintain a broadband connection but have only a single PC.

Thus, if you don't need the extra LAN ports or wireless access a broadband router offers, does it serve any real purpose other than to add cost and complexity? My answer to that question would be a "yes," but before I elaborate further let's briefly review a basic function of the typical broadband router.

To be sure, a router's primary task is to take your high-speed Internet connection and make it available to more than one computer. This is accomplished through NAT, or Network Address Translation. There are several different flavors of NAT, but in this context NAT allows multiple devices on your home network share the single IP address provided by your ISP.

When you use a broadband router with NAT (and virtually all include NAT capabilities) on your home network, the router receives the ISP-issued IP address and your computers are issued unique IP addresses from a specially reserved range of private addresses (most commonly 192.168.x.x).

The router then uses the ISP's public address to communicate with the Internet, and in turn provides connectivity to the systems on your private network by tracking their IP addresses and monitoring traffic so it knows what sites each system is in contact with.

In this scenario, because all of the computers are on a private network that's hidden behind the public IP address, none of the computers are in direct communication with the Internet. Therefore, in addition to connection sharing, NAT provides a basic level of firewall protection because it prevents a computer's IP address from being scanned or from receiving any unsolicited connections. (Traffic coming into the public IP is ignored unless it's in response to a request from a PC on the private network.) In other words, even if don't share your connection because you only have a single PC, a router's NAT function still serves an important security function.

In contrast, when you connect a PC directly to a cable modem or DSL gateway (it doesn't matter whether you do it via Ethernet or USB), it issues its IP address to your system, and when it's a public IP address that system becomes fully identifiable and accessible by other systems on the Internet, leaving it exposed and vulnerable to attack (at least unless you're running a software firewall).

So can you get the benefit of NAT without a router? That mostly depends on your ISP and how its network and/or equipment is set up. Not all that long ago, connecting a PC directly to your ISP-supplied hardware all but guaranteed that your system would have a public IP address this is certainly still the case with my ISP.

It seems that some ISPs are now incorporating the NAT feature directly into the gateway devices they issue to customers. This provides a private IP to the customer's system and keeps the public IP address within the cable/DSL device. The IP address your PC gets when connecting directly to your ISP's equipment determines whether or not NAT is being used. If it's in the 192.168 range, then it supports NAT if it's anything else, you're likely getting a public address.

All of this returns us to the question of whether a router is necessary when you're not sharing your connection among multiple PCs. For non-technical folks, using a router can have a downside as ISPs generally won't provide technical support when third-party hardware is being used on the connection. But nevertheless, if your ISP's equipment doesn't provide NAT, getting it through a router is worthwhile.

Adapted from Practically Networked