What is my IP address?

[relztrah]

When I use whatismyip.com I see an IP beginning with 24. When I log on to my router there is an IP beginning with 10. Why are there two separate IP addresses?

 

[Corday]

Your router IP is assigned to the device you're using by your router. The IP you see beginning with "24" is the public address of your router.

 

[Digerati]

Your router IP is assigned to the device you're using by your router.

Ummm, me thinks Corday might still be a bit decaffeinated this morning. I am on my second mug so I will attempt to explain further.

You did not describe your network setup so I am going to make a big assumption here, only because you said "router" and not "modem".

I am going to assume you are using a "residential gateway" device to connect your LAN or local area network (your computers) to the Internet. A residential gateway device is an integrated network appliance (typically provided by the ISP - internet service provider). This "gateway device" normally includes in one box, at least the modem, a router, and a 4-port Ethernet switch. Most also include a WAP (wireless access point) to provide WiFi or wireless access.

These are 4 "discrete" network devices that just happen to share a common case, power supply, circuit board and often a common menu system. Regardless if using a residential gateway, or discrete devices (I have a separate modem and a "wireless router", for example) they work the same way.

Note the function of a router is to isolate and/or connect two networks. In this case, your LAN and the Internet.

The cable coming from your ISP connects to the modem. Your ISP assigns a "unique" IP address to your modem (and your billing account). In your case, that is the 24.xxx.xxx.xxx number. This is the IP address the rest of world sees as you - your "public" address.

Then the router connects to the modem. If integrated, this connection is internal to the gateway device. If discrete devices (like mine), there will be a separate Ethernet cable connecting the router to the modem. The router then assumes that same unique IP address as assigned to the modem by the ISP.

From there, all the computers and wireless devices in your home (on your LAN) connect to the router either via WiFi, or by Ethernet cable, using unique IP addresses, as assigned by the router (more on that in a minute).

It is important to understand the Internet will not accept more than one connected device with the same IP address. This is because it will not know where to send the data. Therefore, on the Internet side, EVERY DEVICE must have a "unique" IP address.

The problem is, we users in the world have billions and billions of internet connected devices (computers, cell phones, tablets, "smart" thermostats, Ring door bells, security cameras, etc. etc.). We have WAY MORE devices than xxx.xxx.xxx.xxx provides "unique" IP addresses.

So to deal with that limitation, our routers assign unique IP addresses to each of our connected devices. This is typically done via the standard network management protocol called DHCP (Dynamic Host Configuration Protocol). Yet, again, the world only sees the 1 single address assigned by the ISP.

In your case, your router probably assigned something like 10.0.0.2 to one computer and maybe 10.0.0.3 to another and so on. In this way, you can have over 250 devices on your LAN, all with their own IP address. Yet the modem, your ISP and the world only sees the one 24.xxx.xxx.xxx address. The router then keeps track of your devices, which devices is sending data, and to which device received data goes.

Note too, you may have 3 or 4 neighbors (and millions more around the world) who may also be using 10.0.0.2 for their computers. But that's fine because each of their modems have been assigned unique IP addresses from their ISPs.

As a side note, the typical home network is assigned addresses by the router using 192.168.xxx.xxx addresses. The fact yours defaulted to 10.0.0.xxx "suggests" there was, at one time, another router on your network, or for some reason your ISP changed it (if ISP supplied device). No big deal either way, but should you get another router, don't be surprised if all your connected devices suddenly change to 192.168.xxx.xxx.

Anyway, as Corday said, the 24.xxx.xxx.xxx is your "public" address (what the world sees as you). And your 10.0.xxx.xxx address is your private, or local address assigned by your router.

Clear as mud, huh?

There will be a test on this tomorrow.