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How do I know if I'm behind a NAT router?

I’ve seen you talk about NAT routers as firewalls, and so on. How do I know
if I have one?

The answer’s not as obvious as a lot of people are thinking. Yes, much of
the time a NAT router is an additional box … a device that you plug your
computer into that, in turn, plugs into your internet connection. And that box
will typically say “router” on it.

But that’s not the only way you can end up behind a router.

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As it turns out, many broadband modems also act as a router – and
they won’t say it on the outside. Knowing whether they’re acting as a NAT
router is important – you might be able to avoid buying an extra router you
don’t actually need, or you might be able to avoid installing firewall software
you don’t actually need.

Finding out is fairly simple.

My favorite way is to open a Command Prompt – that’s
usually done this way:

  • Click on Start

  • Click on All Programs

  • Click on Accessories

  • Click on Command Prompt

You’ll probably get window similar to this one:

Empty Command Prompt Window

“…many broadband modems also act as a router
…”

In that Window type “ipconfig” followed by the enter key, and you should get
something like this:

ipconfig results

Now, like me, you may have more than one network adapter. The one you
probably want to pay attention to is the one labeled Local Area
Connection
, for wired connections, or Wireless Network
Connection
if you’re running via a WiFi or other wireless
connection.

The line you care about is this one:

"font-family: 'Courier New', Courier, monospace; font-size: larger;">IP
Address. . . . . . . . . . . . : 192.168.1.2

That’s your computer’s IP address. If it begins with “192.168”, as mine
does, then you are almost certainly behind a NAT router. IP addresses that
begin with “192.168” are actually invalid on the internet as they are
specifically intended for non-internet, local networks. The router performs
what’s called “Network Address Translation”, or NAT, to translate from your
local IP address to your internet IP address as assigned by your ISP.

You may also see an IP address beginning with “10.”, or some addresses
beginning with “172.” – these, too, may mean that you are behind a router of
some sort, but these are typically NOT used by modems and consumer-grade
routers. They’re typically used for larger installations such as corporations,
hotels or some ISPs.

So if your computer is connected directly to your broadband modem, and you
have a “192.168.” address, then your modem is acting as a NAT router. If you
have some other address, then it’s not, and you probably want to investigate
installing a NAT router or firewall.

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14 comments on “How do I know if I'm behind a NAT router?”

  1. After reading a few different articles about using routers on your site (and at others), I am STILL confused. Like in your IP Config shown above, I seem to have 2 different IP addresses! I will explain…

    I have a cable modem and router connected to my desktop computer and use the router for wireless internet accesss on my laptop. After reading two of your articles on wireless access, I’m STILL not sure what’s going on! My Netgear shows my IP address as beginning with 192.168, so from what you wrote, I am obviously behind a firewall. However….I have a Google addition on my homepage which also shows my IP address–and this address is totally different and changes every few days. (I believe they do this for security purposes).

    My problem is that when this address changes, I lose my internet connection on the laptop. Unplugging the router for 30 seconds and plugging it back does resolve the problem and my laptop is back online again.

    Why is this happening and can I resolve this problem without having to reboot the router every time this occurs?

    Every article I read is either too technical for laymen to understand or it doesn’t address this particular problem or provide a fix for it (other than rebooting, which is what my ISP and another one of your articles said to do)! But I just can’t believe there isn’t a way to prevent this dropped connection from happening in the first place!

    I would truly appreciate your help because it’s driving me crazy!

    Thank you,
    Gina

    Reply
  2. The only one that comes up for me is Local Area Connection 3. It has the 192.168 IP, so that means I’m behind an NAT Router. I checked by going to whatismyip.com, and it showed a different IP Address.

    Reply
  3. I have dialup and my ipconfig is showing that my ip address is 68.0. isnt that behind a nat router also?? i have dialup though with an internal old modem. i cant use p2p at all because i cant find the config web page to login to. Im pretty sure that i have to be behind a router. is this my isp’s router or what?

    Reply
  4. I need to know the config web login so i can port forward for p2p. I also went on my isp’s webpage and there is a thing on there that says you have to pay$20 extra a month to have a static ip? Im used to dealing with cable n dsl but i just moved way out to the country and i have no other option. any help would be greatly appreciated. thanks

    Reply
  5. —–BEGIN PGP SIGNED MESSAGE—–
    Hash: SHA1

    No, you’re not behind a NAT router.

    It’s important to note that EVERYONE is behind a router – routers are
    the workhorses of internet connectivity, but not all provide the
    NAT/firewall functionality that one would use to protect or firewall
    yourself.

    Your IP address is a “real” internet IP, so you’re connected directly to
    the internet. Your ISP may still be blocking things, I suppose, but
    it’s not a NAT issue. You’ll need to ask them.

    Leo
    —–BEGIN PGP SIGNATURE—–
    Version: GnuPG v1.4.6 (MingW32)

    iD8DBQFF83SyCMEe9B/8oqERAhO0AJ0QKOcl8UQdtvAO/Bxijp3NmsKwzwCePme6
    IyAVoKwEht3AE2/3Oh7ECGA=
    =OPmg
    —–END PGP SIGNATURE—–

    Reply
  6. Hi,
    I’v looked everywhere trying to find some sort of solution for my problem which you’ve probally heard before…let me try to explain it easily..
    I installed a P2P program on my computer called Azureus..it works fine but it is slow probally because my computer is just plain slow and i have dial-up..Later on i installed another P2P program called uTorrent (i read it uses less memory). It tells your to check if port is forwarded properly…I’v tried all types of ports and when i click the button “check if port is forwarded properly” it always gets the error message “xxxxx port does not seem to be open”…i went to port forwarding.com and they talk about things like router and firewall…well, first of all do i even have a router? is router and firewall the same thing? Second of all, if i do have a router, where do i begin to look?..there is no little square box connected to my computer..im so confused…i have so much to ask! let me go on….
    Why is one P2P program working and not the other?..Iv disabled windows firewall because my computer had two firewalls running at the same time…but in windows firewall in the exeptions tab, uTorrent is checked…shouldnt that allow it? my other firewall is for aol and isnt causing problems for Azureus so it shouldnt for uTorrent…how can i get this thing to work without going nuts with too much technical information or making my computer even more slow?…if iv confused you let me know…
    Just to sum it up:
    I have Windows XP home edition
    AOL dial-up internet connection
    Conexant Smart modem
    Disabled windows firewall but allowed uTorrent as an exeption…do i need to open ports through my firewall for it to work? if so which ones?
    thanx a bunch

    Reply
  7. Leo, I read a question that was asked on the “behind a NAT router” page, but I did not see an answer to it. I have been working to resolve the same problem for months, hours and hours at a time. Can you please direct me to a help resource as I have not found an answer yet.
    The question revolved around my wireless Laptop randomly starting to search for an I.P. address only when on my home network when it should already have one. My situation is the same as in the post:

    After reading a few different articles about using routers on your site (and at others), I am STILL confused. Like in your IP Config shown above, I seem to have 2 different IP addresses! I will explain…

    I have a cable modem and router connected to my desktop computer and use the router for wireless internet accesss on my laptop. After reading two of your articles on wireless access, I’m STILL not sure what’s going on! My Netgear shows my IP address as beginning with 192.168, so from what you wrote, I am obviously behind a firewall. However….I have a Google addition on my homepage which also shows my IP address–and this address is totally different and changes every few days. (I believe they do this for security purposes).

    My problem is that when this address changes, I lose my internet connection on the laptop. Unplugging the router for 30 seconds and plugging it back does resolve the problem and my laptop is back online again.

    Why is this happening and can I resolve this problem without having to reboot the router every time this occurs?

    Every article I read is either too technical for laymen to understand or it doesn’t address this particular problem or provide a fix for it (other than rebooting, which is what my ISP and another one of your articles said to do)! But I just can’t believe there isn’t a way to prevent this dropped connection from happening in the first place!

    I would truly appreciate your help because it’s driving me crazy!

    Thank you,
    Gina

    Reply
  8. —–BEGIN PGP SIGNED MESSAGE—–
    Hash: SHA1

    I don’t have an answer for you.

    It sounds like your internet IP address is changing (that’s
    the address your router uses to connect to the internet).
    It’s not uncommon for that to change. It’s not a security
    thing, per se, it just happens.

    The problem is that it shouldn’t matter. Your router should
    just handle it and keep things working properly.

    I suppose you could try another router, but it’s hard for me
    to definitively point a finger at it – could be a
    configuration thing too, I suppose, but I can’t say for
    certain which one without seeing the router.

    Sorry I don’t have more for you.

    Leo

    —–BEGIN PGP SIGNATURE—–
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    iD8DBQFHimUACMEe9B/8oqERAv5mAJ4tCEBuIaKxq2qORoA0Jq5oNt3ZywCfdP8M
    62VlV3Kc708vnd6IHpLPQ0Q=
    =RPji
    —–END PGP SIGNATURE—–

    Reply
  9. hello, i have a router siemens SL2-141.

    i did configure all the ports and stuff, but its a pain in my butt realy, nat makes the network 3 times slower ! i have a static ip adress configured, i have 2 pc’s.

    one: (static)

    10.0.0.2 ip

    10.0.0.138 gateway

    255.0.0.0 netmask

    second (wireless)

    10.0.0.1 ip

    10.0.0.138 gateway (of course its same ^_^)

    255.0.0.0

    now i tried the option to remove nat, which blocks all ports.

    i did connect to internet, but i didnt actually was, but the router kept recieving, but i didnt recieve it…. i was constantly on my static ip that time, if you could help and tell me how to disable it and making the router work, even if i have to change the router gateway, i must turn it off ! its a pain in my behind O_O

    Reply
  10. Reading the screen the Command Prompt brought up, is Ethernet Adapter another name for router? Or a brand of routers? Or something else altogether?

    Etehrnet Adapter is the plug into which your network cable goes into your PC, or the wireless intenet connection in your laptop. It is NOT the router.

    Leo
    25-Feb-2010

    Reply
  11. hy, please help me
    How to test if you were monitored by routher (web history) ?
    We have Linksys WRT 160NL (DD-WRT v24-sp2 (03/19/12) std)
    Is there a way to see router settings withaut password, withaut function to change enything , y yust want to see if there was enebled logs ?
    will program ultrasurf help me ?

    Reply

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