Indeed it does.
It’s an important part of understanding how information travels between your computer and the internet services you use.
It’s also important to know when asking questions and interpreting answers.
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Your router’s primary job
Routers perform many different functions, but their primary role, at least in the home, is to act as a gateway to the internet.
You can think of your router as having two “sides”: one side is connected to the internet, and another to all of your computers and other devices. The router sits in-between, passing data traffic back and forth.
The internet side is a connection provided by your ISP. All traffic to and from internet sites and services travel over this connection.
The “local” side, often referred to as a LAN, for Local Area Network, consists of all of the devices connected to the network at your home or place of business. Be it through a wired or wireless connection, these devices connect not to the internet, but to your router, through which the internet is made available.
The router’s two networks
These two networks — the internet on one side and your local network on the other — are completely separate. That data crosses between them is only due to the workings of your router, which is connected to both.
Two different networks imply two different IP addresses.
On the internet side, your router is typically assigned an IP address by your ISP when it boots up or first connects. This is your “true” internet address. You can see what yours is by using several online services, or by consulting my article, What’s My IP Address?
On the local side, your router is configured to use a specific IP address: often something like 192.168.1.1, 10.1.10.1, or something similar. You can see what yours is by running the command “IPCONFIG /ALL” in a Windows Command Prompt and looking for the Default Gateway address.
The number using periods as the separator — it’s IPv4 address1 — is the IP address of your router.2
Your router’s other job
Another job performed by your router is to manage the local network.
When the router connects to the internet, it requests an IP address, which is then provided by the ISP. This is your internet IP address. You very likely have only one of these, and it’s assigned to your router.
When your computer (or other device) connects to your local network, it also requests an IP address. This IP address is provided by your router. It looks a lot like the router’s own local IP address, though the last two numbers will be different. This is that computer’s local IP address. Each device connected to the local network has its own unique local IP address.
When a device on your local network wants to communicate with a device on the internet, it is the router’s job to “translate” between the two types of addresses. In fact, that’s what it’s called: Network Address Translation, or NAT. NAT makes it appear as if all of your devices (each with a unique local IP address) are coming from the same internet IP address — because they are. All the traffic going to and from the internet is handled by your router through its internet-side connection and IP address.
Determining the IP address
As we’ve seen above, there are two ways to see the two different IP addresses:
- Using an online service (or page like my What’s My IP Address? article) will tell you the internet IP address of your router. When someone asks you for your IP address — say when trying to diagnose an issue you’re having in accessing a website — this is the number you provide.
- Using the “ipconfig” command in a Windows Command Prompt will tell you the local IP address of that computer. In practice, you rarely need to know this one, except perhaps when diagnosing local network connectivity problems.
Specific IP addresses
One final note: a “local” IP address begins with either:
- 10.x.x.x
- 172.16.x.x through 172.31.x.x
- 192.168.x.x
You will never see these addresses on the internet. They are called “non-routable” IP addresses and are reserved exclusively for local networks. That’s how, if you provide the wrong kind of IP address to your support person, they can tell immediately and ask you for “the other one.”
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Just about every home router I’ve come across uses the Class C private address space; I’ve been thinking about using a Class B, just to provide some confusion to an ambitious hacker. Is there any reason to wonder whether the router manufacturers will truly support it?
Depends entirely on the router. Mine defaults to class A for example. I suspect it’ll do nothing to impact a hacker, though.
Some router manufacturers use the Class A private address space [10.x.x.x] and others use the Class C address space [192.168.x.x]; I’ve never seen one that uses the Class B private address space [172.16.x.x – 172.31.x.x] but actually they can officially use any of the A/B/C private addresses and possibly allow you to use any address range you choose. You can change the addressing range of the LAN side of the network using the DHCP addressing option in conjunction with an address change of the router itself [you’d typically want the router to give out addresses that match, but don’t include, its own]. The limits will be defined by the software that runs on the router; some may limit you to a subset of the legitimate addresses for reasons best known to themselves; others may allow you to use any valid IP address range.
I’m not sure there’s any benefit in doing this change though as ‘hackers’ shouldn’t be able to ‘see’ the LAN side addresses anyway! If they can, you’ve got a worse problem.
Postscript to the above:
I’d never tried before but I used my ‘spare’ NetGear WNR220 router to test the following LAN side address changes [these are the addresses ‘dished out’ to devices that connect to this router]:
1) Changing the LAN address to 172.16.1.1 and the DHCP range to 172.16.1.101 – 200. These addresses are non-routable Internet addresses designed [and thus ‘allowed’] for use on customer connected LAN Routers.
2) Changing the LAN address of the router to 20.1.1.1 and the DHCP range to 20.1.1.101 – 200. These are Internet addresses ‘owned’ by the US based DXC Corporation for their use for Internet connected devices [and thus ‘not allowed’].
In both cases, the NetGear router allowed me to enter the data in the screen fields and successfully rebooted with the revised addresses and allowed me to connect wirelessly to the router. Note: while ‘not allowed’ by Internet rules, the NAT [Network Address Translation] in the Router doesn’t allow these addresses ‘out’ anyway; they’re purely for internal use by my devices on my router’s internal LAN.
lEO, I AM NOT REALLY VERY COMPUTER LITERATE, BUT I SEEM TO HAVE NOTICED SOMETHING THAT IS BOTHERING ME. IS GOOGLE REALLY TRYING TAKE OVER ALL EMAIL. I JUST SEEM TO SEE GOOGLE WILL HELP YOU HERE AND THERE, INPUT THIS AND THAT TO GOOGLE! WHICH MEANS TO ME YOU ARE GOING TO BE USING GOOGLE.
I DO NOT LIKE THEIR NEW EMAIL SYSTEM. SO I HAVE LEFT ONE ONLY ONE ADDRESS THERE (WHICH I TELL NO ONE ABOUT.) I DO NOT WANT TO USE GOOGLE 100% AND HAVE PUT THE ONES I USE IN THE ORIGINAL PLACE. OF COURSE, PART OF MY PROBLEM IS THAT I COULD NOT GET THE NEW GMAIL TO ACT AS IT IS SUPPOSED TO DO.
I’m not really sure what it is you’re asking, but Google does provide a very robust email system that I both use and recommend myself. They’re not trying to “take over”, as you put it, they’re simply putting out a good product.
Not sure I agree with you on this one Leo. I’ve been in IT about as long as you have [started on COBOL for an Insurance company in July 1975] and I’ve seen Google develop from a useful search engine [which I still use] in the early part of this century to a dominant force [only slightly behind Apple] in the now much enhanced and changed IT marketplace.
Google has been dominant in the email marketplace, not rightly, in my view [its email concepts are a bit non-standard] and partly because its dominance allows it to ‘require’ gmail accounts to use some of its, admittedly useful to some, facilities such as Android and YouTube.
Very good idea of an article, if I’m allowed to say. Small, “obvious” things that are anything but.
Well, Leo, I believe Google are doing more that simply providing a good product. When we use their products and services, they can capture a lot of data about us and our behavior on the internet. They aggregate this data and sell it to advertisers. This is their business model, and it is the “price” we pay for their “free” products and services.
Thank you Leo for this report!! I had no idea that my router had 2 IP addresses!! It was to say the least very confusing at first! Once again a great report!!!
Hi Leo,
I just had a new internet service installed so I could use internet TV. I could not pick up one of the local channels I was supposed to be able to access for live TV.
Hulu told me the IP address was for a different city in my state and that is why I couldn’t get the local channel. The internet provider told me to reboot the modem several times to get a new IP address. I rebooted 3 times but still could not get the channel. The internet provider told me I could request a static IP address but would have to pay for it (I have to contact customer service to see what the cost is). Does this sound right to you? It sounds like if my power goes off I might not have the ‘right’ IP address when I reboot. Do most people have to pay for a static IP address to use internet TV?
No, most people don’t, but then most people aren’t fighting to get a local TV channel like that. If the local TV channel access is restricted based on IP for you I’m not sure of another solution.
Leo, I am having an issue connecting my printers, all 3 are Canon. The router is assigning 192.168.5.xx and the computers are 192.168.0.xx. Canon tech says the reason the printers won’t work is that the ip addresses are compatible between the computers and the printers. How can I fix the issue?
Sounds like you’ll have to dig into your router settings, or perhaps explain a little more about your network setup. Looks like they’re getting treated as if they’re on two completely separate networks.
I have 7 ip cameras in my house my daughter views these cameras from her house but at times they freeze up
We’d need a LOT more details about the problem, for example: which version of Windows you are running, which program are you having the problem with, what were you attempting to do and the EXACT error message(s) you were getting. Please read: What Information Should I Provide When Asking for Help?
https://askleo.com/information-provide-asking-help/
Thank you for clarifying the vital distinction between the upstream and downstream IP4 addresses, which was not evident on the Vodafone helpline ; and the fact that different devices on LAN have their own.
I had also been advised to enter the IPv4 manually but this seems more hazardous , with the need to know the DNS gateway numbers and servers. Further it is still not clear whether in WIndows10 on manual entry whether to enter the Internet iPv4; must be but what I see from the pre-existing look like LAN addresses.
Good afternoon. Can you tell me that if I have received two emails near enough around the same time and both originating ipv6 public addresses have the first 4 components the same but the other 4 are different. Does this mean they are from the same router or different routers. This is not the internal/private number.
Thanjs
I don’t believe it’s possible to tell. Sorry.
Greetings all.
I need help with resolving a constant interruption/disconnect between Netgear ProSafe switch and 2 identical WIFI routers. This setup has been suggested by Netgear Tech support. I am by no means a IT blessed person but I do understand some basics.
SETUP:
– Internet service by Spectrum via Hitron Technologies E31N2V Router.
– Above Router feeds a Netgear FVS318G Firewall-Switch (8 ports) via a short Cat6 cable.
– From this Firewall-Switch there are 2 identical Netgear NightHawk RAX75 WIFI Routers via Cat6 cable connected. (IP for router downstairs is 192.168.1.1 and router upstairs is 192.168.10.10, both are DHCP enabled)
ISSUE:
On a very regular basis we cannot connect to either WIFI router. The SSID’s are visible but no connection can be established. To resolve the issue I have to go power down/up all equipment (Spectrum router/Firewall Switch/both WIFI routers)
I have called Spectrum and Netgear and each blame the other for the issue. Would anybody out there be able to steer me in the right direction to resolve this annoying issue.
Thank you.
Steve