Internal and External IP Address Query

[exchemist]

I was trying to find out my IP address, as a question to put to scammers calling me to tell me there is something wrong with my computer (heh heh, that should fox them). However I am now confused. I read there is a public, or external IP address, which seems to identify the WiFi router for the house and then individual, internal IP addresses for the various devices (laptop, tablet, phone) that communicate with the router. So far so good.  

I've found the internal address on my laptop, but when I look up the external one using whatismyipaddress.com , I get different answers for the laptop (Mac) and the tablet (iPad). Furthermore, the answer I got today for the iPad doesn't seem to be the same as when I tried this a couple of days ago, though it could just be my poor memory. 

At all events, from what I have read I would have expected the public, external IP address to be the same for everything using the same router. Is this not the case?  And should this external address be permanent, or does it change when you reconnect each time or something?

 

[swansont]

2 hours ago, exchemist said:

And should this external address be permanent, or does it change when you reconnect each time or something?

It’s probably a dynamic IP address assigned by your service provider, so it can change. 

 

[exchemist]

15 minutes ago, swansont said:

It’s probably a dynamic IP address assigned by your service provider, so it can change. 

 

Interesting. Do you know what causes it to change?

[zapatos]

2 hours ago, exchemist said:

Interesting. Do you know what causes it to change?

It is often done to keep scammers from targeting a network. It also allows IPs to be reused rather than have them wasted when you toss out your old device.

Edited August 7 by zapatos

[exchemist]

1 hour ago, zapatos said:

It is often done to keep scammers from targeting a network. It also allows IPs to be reused rather than have them wasted when you toss out your old device.

OK thanks. So I need to check every so often to make sure I know the one in operation.

What about the other question: the reason my various devices seem to have individual public IP addresses, even though they are all fed by the same WiFi router? I had perhaps naïvely imagined the router would have a single address and that it would take care of sending the right data to the right device if several are connected. Is that not how it works? 

 

[Mordred]

Not quite the router will have its own address but so does each device downstream. The router will rebroadcast the data included the IP  address which is contained with each data packet.

The device that has the correct address will then pick up the data.

If you do not know the IP address on the CPU should be a MAC number. You can use the old DOS (ARP) command using the MAC Addy and return the IP address. Or change that IP address.

There are utilities though available that does the same thing however I can't recall the name.

 

Edited August 21 by Mordred

[exchemist]

32 minutes ago, Mordred said:

Not quite the router will have its own address but so does each device downstream. The router will rebroadcast the data included the IP  address which is contained with each data packet.

The device that has the correct address will then pick up the data.

If you do not know the IP address on the CPU should be a MAC number. You can use the old DOS (ARP) command using the MAC Addy and return the IP address. Or change that IP address.

There are utilities though available that does the same thing however I can't recall the name.

 

Thanks, that seems clear enough. I have found the internal and public addresses of the laptop. For completeness, do you know how I can get the IP address of the router? 

[exchemist]

1 hour ago, Mordred said:

Not quite the router will have its own address but so does each device downstream. The router will rebroadcast the data included the IP  address which is contained with each data packet.

The device that has the correct address will then pick up the data.

If you do not know the IP address on the CPU should be a MAC number. You can use the old DOS (ARP) command using the MAC Addy and return the IP address. Or change that IP address.

There are utilities though available that does the same thing however I can't recall the name.

 

Sorry ignore last query, I've found Alt key + clicking on Wifi icon reveals it.

So now I am armed with the "innocent" questions to ask any telephone scammer claiming there is a fault/malware on my computer or router, heh, heh. 😁 

Edited August 21 by exchemist

[Mordred]

No problem glad to help.

[studiot]

3 hours ago, exchemist said:

So now I am armed with the "innocent" questions to ask any telephone scammer claiming there is a fault/malware on my computer or router, heh, heh. 

I usually have a nice chat with those nice people from Microsoft, British Telecom, British gas, etc whcih runs along the lines of

Them "We're from British Bullshit dot com abbout you  router, pc, telephone......"

Me "Oh good when's the engineer coming to fix it?"

Them " Uh What"

Me " your are calling to make an appointment to fix the fault right? It's over week since I reported it."

 

yada yada

 

[exchemist]

4 minutes ago, studiot said:

I usually have a nice chat with those nice people from Microsoft, British Telecom, British gas, etc whcih runs along the lines of

Them "We're from British Bullshit dot com abbout you  router, pc, telephone......"

Me "Oh good when's the engineer coming to fix it?"

Them " Uh What"

Me " your are calling to make an appointment to fix the fault right? It's over week since I reported it."

 

yada yada

 

Yes, my plan is to say "Just to start by checking we are talking about the right computer, what's the IP address of the one with the fault that you are referring to?"

Probable answer: "Click....dzzzzzzzzz........."

But if they come back with a series of numbers it won't bear any relation to the real ones - I hope! 

Edited August 21 by exchemist

[studiot]

23 minutes ago, exchemist said:

Probable answer: "Click....dzzzzzzzzz........."

Good start, although you need a good answer if they already have it.

You'd be suprised how much of their time you can waste with unexpected responses like yours or mine.

I do like to put as big a spoke as possible into their machinations.

[exchemist]

37 minutes ago, studiot said:

Good start, although you need a good answer if they already have it.

You'd be suprised how much of their time you can waste with unexpected responses like yours or mine.

I do like to put as big a spoke as possible into their machinations.

Yes occasionally I play it for laughs. Sometimes I put on a fake Indian accent (which I can do from my time in Dubai) and start arguing with them in the Indian style. Sometimes I ask the if they really enjoy a job in which they have to lie all day long.  But it doesn't do to be abusive, since they can retaliate by ringing up in the middle of the night. My late father was the last person to call me on the land line so when the land line goes I'm almost sure it will be a scammer.

[Sensei]

IP address can be public or private.

IP address can be static or dynamic.

So we have four combinations: public static, public dynamic, private static, private dynamic.

 

IP address can be in version v4, or in version v6.

IPv4 is four decimal numbers separated by dots.

IPv6 is many hexadecimal numbers separated by a colon. Be careful with these. They can encode a MAC address of a real machine, which can uniquely identify a person worldwide.

 

A home computer with a WiFi card or a smartphone/tablet connected to home WiFi router with plugged modem, most likely has a private dynamic IP address assigned by DHCP. This will most likely be 192.168.0.x, where x is from 2 to 254 (because 0 and 255 are special purpose, and 1 is usually router). or 192.168.y.x (y=0...255).

If you use Android smartphone as hotspot, your IP will be something like 192.168.43.100 or so.

https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol

 

If you connect the modem directly to your computer and your ISP is cool, you may have a public static IP address or at least a public dynamic IP address. Doubtful. Nowadays ISPs are screwing people over and such options are only for enterprises for more $$$..

 

You can check your IP addresses (yes, addresses! You can and will have multiple IP addresses!) by Start > cmd.exe and then ipconfig /all (on Windows), or ifconfig (on Linux).

A typical computer (whether or not desktop or laptop) has at least 6 private IP addresses. 127.0.0.1 (IPv4 localhost) ::1 (IPv6 localhost), 192.168.x.y (IPv4 ethernet card) some IPv6 for ethernet card, 192.168.x.y (IPv4 wifi card) and some IPv6 WiFi card. If you will plug more modems or external WiFi USB, you will have more..

 

What showmyip.com etc. shows is IP address of your router/modem, or even your ISP IP address. Multiple people can have it. Once you have it, paste it here https://ipinfo.io/

 to learn what is ASN.

IP address with a slash like /16 means 16 bits are zeroes in the mask i.e. mask is 255.255.0.0. /8 means mask is 255.0.0.0 etc.

 

If you have public static IP address, you can go to router configuration (typically in a web-browser open http://192.168.0.1 (no SSL!!! manually edit if needed) ) and configure port forwarding to your real machine.

Install XAMPP on your desktop/laptop, configure port 80/443 forwarding to your private static IP (disable DHCP/configure DHCP to make your IP private static), and ask a friend (or use smartphone with LTE/5G) to visit your web server.

https://www.apachefriends.org/pl/index.html

(This way you can share things with other people/friends/family, with a higher level of security than sending them via email or to the cloud.. which is one of the most stupid things people can do. Sextels of Hollywood actresses came from the cloud. Their cloud)

 

On 8/7/2024 at 1:27 PM, exchemist said:

Interesting. Do you know what causes it to change?

They want your money to make it static (so you'll have less trouble installing some server at home).

 

On 8/7/2024 at 4:02 PM, zapatos said:

It also allows IPs to be reused rather than have them wasted when you toss out your old device.

Hundred or thousands of people share the same IPv4 address at the same time.. There is only 2^32 = 4.3 bln IPv4 addresses. Some not assigned, reserved, special purpose.. People have a couple smartphones, a couple computers, a couple of tablets, a couple of laptops etc. Every IoT device (e.g. camera, payment terminal) can have a separate SIM card.. Owners want/need to have their IPv6 address to connect them.

 

IPv4 was exhausted in 2011.

https://en.wikipedia.org/wiki/IPv4_address_exhaustion

 

 

  

On 8/7/2024 at 5:27 PM, exchemist said:

OK thanks. So I need to check every so often to make sure I know the one in operation.

Run this command in a loop in a script:

wget -q -O- http://ipecho.net/plain

With some delay, such as 15, 30, 60 minutes after each check.

 

 

  

On 8/7/2024 at 5:27 PM, exchemist said:

What about the other question: the reason my various devices seem to have individual public IP addresses, even though they are all fed by the same WiFi router? I had perhaps naïvely imagined the router would have a single address and that it would take care of sending the right data to the right device if several are connected. Is that not how it works? 

If they are really using a home WiFi router (and then, f.e. fiber cable), they should have the same IP address (as reported by showmyip.com, etc.) as all other devices using the same Internet connection (as long as you check things within a couple minutes, not hours or days). You need to check this. Once you see the IP, check each one individually in ipinfo.io )

 

8 hours ago, Mordred said:

If you do not know the IP address on the CPU should be a MAC number.

The MAC address (BTW, it has nothing to do with Macintosh) is on the Ethernet card or WiFi card. Each of them is different. So you can have many different MAC addresses.. as many as network interfaces..

The arp command is used to display the MAC addresses of other machines on the LAN. Your machine is not included.

On the Linux you do first e.g. nmap 192.168.0.0/24 and then arp. Otherwise some devices may be missing (and they will be if they have disabled ICMP)

Edited August 22 by Sensei

[Sensei]

On 8/7/2024 at 5:27 PM, exchemist said:

What about the other question: the reason my various devices seem to have individual public IP addresses, even though they are all fed by the same WiFi router? I had perhaps naïvely imagined the router would have a single address and that it would take care of sending the right data to the right device if several are connected. Is that not how it works? 

If you use Tor, the IP address of the Tor server will be displayed by showmyip.com, etc.

If you use HTTP proxy, SOCKS4/5 proxy, the IP address of the proxy server will be displayed by showmyip.com etc.

If you use VPN, the IP address of the VPN server will be displayed by showmyip.com etc.

If someone hacked into your computer and passed the transmission through their computer (to intercept and change TCP/IP/UDP packets), you won't see the correct IP address..

 

 

Edited August 22 by Sensei

[toucana]

On 8/7/2024 at 9:50 AM, exchemist said:

I was trying to find out my IP address, as a question to put to scammers calling me to tell me there is something wrong with my computer (heh heh, that should fox them). However I am now confused. I read there is a public, or external IP address, which seems to identify the WiFi router for the house and then individual, internal IP addresses for the various devices (laptop, tablet, phone) that communicate with the router. So far so good.  

I've found the internal address on my laptop, but when I look up the external one using whatismyipaddress.com , I get different answers for the laptop (Mac) and the tablet (iPad). Furthermore, the answer I got today for the iPad doesn't seem to be the same as when I tried this a couple of days ago, though it could just be my poor memory. 

At all events, from what I have read I would have expected the public, external IP address to be the same for everything using the same router. Is this not the case?  And should this external address be permanent, or does it change when you reconnect each time or something?

 

A typical home WiFi router makes use of something called DHCP (dynamic host configuration protocol) to assign LAN (local area network) addresses to all the different devices logged into your home network.

These LAN addresses usually take the form of IP quads formatted as 192.168.x.x  where the 192.168. prefix is a special index which is only valid as an address on a local network -  i.e one that can’t be reached directly from the WAN (wide area network) or the public facing side of the  internet. The router’s DHCP protocol assigns these local LAN addresses to your devices on ‘leases’ which are time limited and can expire. This can be one source of confusion -  if a lease expires, and/or a new device is added to your local network, and the DHCP process bounces these 192.168.x.x values around, it will unexpectedly assign a new address to a particular device. Your home router has an internal address table of all currently connected devices on your LAN that you can inspect.

Home routers also make use of something called NAT (network address translation) which usually works in conjunction with its protective firewall and TCP Port numbers. The latter are used to ensure that incoming data packets from the internet reach the correct device on the local network. You can set up NAT ‘Port Forwarding’ rules in your router to ensure that particular services/message types are routed to one specific device on your local network.

The public facing WAN address of your broadband home router is assigned by your ISP (internet service provider) and should in theory  be static - i.e unchanging. When I first got home broadband, I was given a static public IPv4 address which didn’t change for the next 17 years. Unfortunately that ISP went out of business last year, and we switched to a new provider whose ‘Static’ public IP addresses turned out to be anything but static - they seem to change every time the router is rebooted, or receives a software/firmware update. My new router has now changed its public IP seven times since being installed last December.

The amount of time you are likely to spend fiddling with such networking details depends on quite what you normally do with your home computers. I’m a long-time IRC user and Eggdrop channel protection bot admin - and those ancient things are hell on wheels to configure correctly behind a home router  if network IP values start changing under your feet. You wind up getting a crash course in TCP networking theory !

 

[TheVat]

I've heard the DHCP lease time in the US is about 7 days.  Normally, when it cycles, you will get the same IP address you had reassigned to you.  If anyone actually wants to change their IP address, the trick is to know your ISPs DHCP lease cycle and then shut off your router that day.  This will prevent the "static" option, because the router will be offline and can't get that reassignment. So you will get a new one when you switch back on, and voila, dynamic IP.  (the easy way is to shut off wifi when you go on vacation, which is also a good idea for general security)

IPv6 uses 128-bit addresses, theoretically allowing 2¹²⁸ addresses, which is somewhat reassuring as far as future address exhaustion is concerned.  

[swansont]

This came up in another thread earlier this year. You can force the lease to renew; in Windows you go to the command prompt and type ipconfig /renew, though it’d possible you are assigned the same address.

[toucana]

There was a geek T-shirt joke about this topic

151.194.25.39             —> is a Public IPv4 address quad.

127.0.0.1                      —> is the special ‘Loopback’ address for your own computer on a LAN.

19:08:AF:51:11:08       —> is the MAC or ‘Ethernet’ hardware address of your device in hexadecimal.

[Sensei]

19 hours ago, swansont said:

This came up in another thread earlier this year. You can force the lease to renew; in Windows you go to the command prompt and type ipconfig /renew, though it’d possible you are assigned the same address.

The proper procedure is on Wikipedia https://en.wikipedia.org/wiki/Ipconfig

"An important additional feature of ipconfig is to force refreshing of the DHCP IP address of the host computer to request a different IP address. This is done using two commands in sequence. First, ipconfig /release is executed to force the client to immediately give up its lease by sending the server a DHCP release notification which updates the server's status information and marks the old client's IP address as "available". Then, the command ipconfig /renew is executed to request a new IP address.[3][4] Where a computer is connected to a cable or DSL modem, it may have to be plugged directly into the modem network port to bypass the router, before using ipconfig /release and turning off the power for a period of time, to ensure that the old IP address is taken by another computer.[5]"