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Routers and modems perform different functions and often come combined in one unit. I walk through the functions of a router and how you can tell which one you have.

I have Windows 7 and have always had a router between the modem and the computer. I found that the router was not working and had it checked out and ended up throwing it away as its life had ended. They tell me that I do not need one as the Shaw modem has a firewall and Windows 7 also has one. I also have Norton and therefore, I'm wondering if that's all I need. I'd rather have overkill, but if not required, would just use the modem. I hope you have time to give me your opinion. The modem that I had was a D-Link.

In this excerpt from Answercast #42, I look at the security that a router gives to your system and how routers are often combined with modems from your ISP.

Routers and Modems

So there are a couple of terms getting thrown around here that I want to be clear about. A modem and a router are two different things.

  • The Shaw modem that you have may, in fact, be a combined modem and router.

  • It's not uncommon.

It might be a router

I can't say that it happens in most cases, but many ISPs provide a single box that is both a modem and a router in a single box. In fact, there are some that will provide you with wireless: a modem/router/wireless access point.

So, if what you are calling a modem is in reality a combined modem and router, then no, you don't need another router.

The fact that they say it has a firewall leads me to believe that might be exactly what it is.

It might just be a modem

If on the other hand, what you have is pure modem and not actually a router:

  • I then suggest that you go ahead and replace the router that you've discarded.

It doesn't have to be an expensive device. Any kind of a DSL/broadband router should give you the protection that I look for from a router and the router's firewall.

Software firewalls

A router is somewhat different than Windows 7 firewall; not that Windows 7's firewall isn't good, but a router that is not part of your computer is inherently slightly safer than a firewall that is part of your computer.

  • The router actually prevents a certain class of threat from reaching your computer at all.

  • Whereas, when the Windows 7 firewall is relied on, you're relying on the computer to protect itself.

Usually, that works. Like I said, the Windows 7 firewall is a good one. But there are definitely known threats that do things like disable the firewall specifically for malware to be able to get in.

Is it a router or not?

So, how do you tell? For one thing, you haven't indicated what the model number of your modem is. That would be the very first thing I would do.

Just Google that model number or look it up on the Shaw website (if they have information) and see if it refers to it as:

  • A modem;

  • Or a combined modem and router.

  • Sometimes, they'll just talk about it as a router.

In any case, as long as the word "router" is used, you're good. If they talk about it as just a modem, then I would not necessarily rely on it also being a router.

Assigned IP address

You can tell on your PC – if your computer has been assigned an IP address that begins with 192.168, then you are almost certainly behind a router. Those are the IP addresses that are assigned by routers.

In fact, those IP addresses are not allowed to be routed on the internet itself. They are, by definition, IP address that only appear on computers or on local networks; the local network side of a router. So that one will tell you for sure.

If you get what would otherwise be a valid internet IP address, then your modem is not acting as a router. That would tell you for sure.

So if you have a combined modem/router, you're done. If your modem is just a modem, I still suggest getting yourself a router.

Next from Answercast 42 – Should I disable gadgets for security?

Article C5673 - August 8, 2012 « »

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Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

Not what you needed?

3 Comments
Lloyd J
August 10, 2012 8:53 AM

Another address you may also see is 172.16.x.y through 172.31.x.y which like 192.168 is non-routable. Most of my clients with 2Wire boxes, unless a setting has been changed, have addresses of with 172.16.1.x

Scott Currier
August 10, 2012 8:59 AM

It may be helpful to check your outside or WAN ip address using a website such as www.myipaddress.com or similar site. You can then compare that with the address of your computer. To get the address of your computer you can open a command prompt and type in ipconfig and the address will be displayed.

If they are the same then your modem does not have a built in router or if it does, it's disabled.

If your local computer has an address in the following blocks....

10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255

there is a router built into the modem and it's turned on.

If your modem has four ports on the back then you can be sure that it has a router built in. However, I have seen many 1 port devices also have a router built into them as well.

My preference is to have the modem in bridge mode, disable router and firewall, and to use a router/firewall/Wireless AP of my own choosing.

At times this is essential because I need VPN capabilities.

Glenn P.,
December 18, 2012 11:46 AM

For Scott Currier:

I didn't quite understand that. Entering ipconfig in a DOS window on my WinXP Pro SP3 box, yields:

18-Dec-12 14:22:41.89
C:\> ipconfig

Windows IP Configuration

Ethernet adapter Local Area Connection:

        Connection-specific DNS Suffix. . . :
        IP Address. . . . . . . . . . . . . . . . . : 10.0.0.3
        Subnet Mask. . . . . . . . . . . . . . . . : 255.255.255.0
        Default Gateway . . . . . . . . . . . . . : 10.0.0.1

        ------------------
Does that signify a router, or not? And if it signifies a router, how do I access its settings page so that I can be sure that they are correct?

(P.S.: Sorry for any icky formatting -- this editor doesn't support fixed fonts!)

A 10.*.*.* address implies you are behind a router, yes. That's a private network, and an IP address that will not be seen directly connected to the internet.
Leo
19-Dec-2012

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