What do the groups of numbers mean? Does your IP address change even if your computer doesn’t move? I have a laptop–if I take it across town or across the country, does my IP address change?
You can think of your IP address as a phone number. Yes, it can change without your computer hardware changing.
The way it works is your computer’s network card/chip has an address called the “MAC address”, which does not change. When you connect it to a network your computer sends a broadcast message (to all nodes on your local network, usually it will be the router that responds) asking for an IP address.
So if you change networks your IP changes.
Just like a phone number the routers on the network will use the IP address to find your computer.
The internet is a network of connected networks. The first part of an IP address identifies which of those networks a computer is in, and the second part is the individual address of a computer within its network.
It’s a big subject, but that’s the gist of it. Take www.google.com. Right now, I’m getting an address of 74.125.230.145 for that. 74.125 identifies Google’s network, 230.145 is used internally by Google to identify the server.
Where it gets a little more complex is when you are using “private” IP addresses, such as the ones that start 192.168. You could have such an address on your home network, move to the other side of the country, and have a very similar or even the same address on a network there. But the public address of the network you are ultimately connected to would be different.
And, generally speaking, the IP address that is used to “find your computer” is usually the IP address of the Cable or DSL modem/router. The IP address of your computer is actually duplicated many millions of times the world-over; it’s only unique behind your router. Of course, this isn’t true if you only have a single machine connected to the internet, but for most people, they run a small private network behind a router, and the router’s IP address is the one that is the “public face” that the internet sees. All machines behind the router share this IP address, and are assigned private IP addresses (usually in the range of 192.168.x.x).
ETA - Ximenean made the same point.
Okay, but my phone number doesn’t change with every cell tower the phone uses.
This statement is ambiguous. Does this mean asking for the network’s IP address or asking to be assigned an IP address? (I think it was this kind of ambiguous language that made setting up wireless networks such a pain in the ass in the early days.)
Again, does this mean my computer can have various “phone numbers”? Because my phone can’t switch between phone numbers on a routine basis. I can’t dial out of my phone at one moment from one number, and then dial out the next minute with a different number without having the phone company change the service.
And (for law enforcement issues) doesn’t this all mean that if you really need to identify where something originates on the internet, you should use the MAC address? Isn’t that really more like the true finger print of who (which machine) originally sent the data?
The MAC address ( hard-coded identifier of the network card) is only for local networking.
The IP address is supposed to be world-wide identifiable.
You hear about routers, which send traffic to where it needs to go. They determine the destination based on IP address. To pull numbers out of thin air, let’s say PacBell owns 142.x.x.x; they would assign 142.0.x.x through 142.20.x.x to San Francisco. 142.20.10.x would be a neighbourhood there. Each person’s home DSL modem that logs on in that neighbourhood grabs one of those addresses. Each number can be 0 to 255 (one byte).
As a result, the rest of the world does not need to know how to find your IP address. Outside of PacBell, other sites like Yahoo or Google just know, “If it starts with 142 give it to one of the PacBell gateways”. The top level routers only have to know a few hundred main routers. Inside, it’s a top-down structure. It is possible to have 2 different locations - let’s say, 143.20.x.x is in Mexico and 143.21.x.x is in Singapore. Routing technology is very flexible. However, the better the “route aggregation” the simpler the process so the internet gods keep the fragmentation to a minimum when they can. SO the first part of the answer to your question is, the IP address is detemined by where you connect to the actual internet. Change location or provider, and your internet address changes.
You see the problem - 4 bytes is 2^32 possible addresses maximum. It sounds like a lot, but many are wasted (broadcast addresses, etc.) The nuber sounded inifinte when it was set up in the late 70’s and a university was lucky to have a few dozen computers. Now, we are running out.
Often machines are coming and going, turning on and off randomly; unless they provide a service, they probably don’t need a fixed address. There’s a service called DHCP that runs on most networks for regular PC’s - it hands out an IP address on demand, then gives it to someone lese once you disappear.
The biggest trick is called NAT - Natural Address Translation. In an office, you don’t need a fixed internet address; you go out to the internet, the internet does not generally come looking for you. So to save addresses, the firewall to the local network gets a real intenet address. A couple of addresses - usually 192.168.x.x and 10.x.x.x - have been designanted as “non-routable”. They don’t work on the internet and are used for internal networks. Your inside network hands out one of these, with the “default gateway” usually the address of your firewall/router (a firewall generally is a router). When you want to do something on the internet, the firewall translates to make your request seem as if it came from the firewall. It does this for everyone inside; so if you and your buddy both open a window to facebook, on the internet it sort of looks like someone at the same address has opened two browser windows at the same time. So a work environment with 100 computers might use only 1 IP address.
(Even so, we are almost out of IP addresses)
This is the second half of the OP question. You can go from home to Starbucks and still have the IP 192.168.1.101 - not because your IP stayed with you, but because Starbucks and your home router use the same internal address range and by luck of the draw, DHCP gave you 101 in both places.
To find your local (internal network behind firewall) IP address, open a DOS box (start-run - CMD) and type the command ipconfig
To find your internet address, go to http://whatismyip.org/
That’s true. It’s kind of a dumb analogy. Phone numbers and IP addresses are meant to do pretty different things.
Your computer is asking a router on the network to assign it an IP address. The protocol used for this is called DHCP. It’s not necessary, though. Before DHCP, you just kept track of your network’s IP addresses manually and configured each machine yourself. You can still do this if you want.
At a given time, your computer can have an IP address for every network interface it has. Got two Ethernet ports and a WiFi card? You can have three IP addresses, assuming they’re all connected to something.
Yes. But the MAC address is not transmitted over IP networks like the Internet; it’s only useful on the lower-level local Ethernet. And non-Ethernet networks do not have MAC addresses at all, although they’ll typically have some sort of local addressing scheme, which may or may not be dynamic. For example, AppleTalk adaptors would generate their own network address upon startup.
The underlined is me. I have one laptop computer connected to the internet with a Sprint aircard. No home network. My TV is not connected to the internet. The only connection is my aircard (and my phone, of course, which is separate).
In this case, your machine (most likely) has a unique IP address. I say “most likely” because I know of some GSM modems that distribute private IP addresses to their clients, and then run a “tunnel” that acts as a router. If I had to bet, I’d say that you have an IP address that rarely changes. You can determine it my looking somewhere in the Network settings control panel, and looking at the properties of your active network connection (I’m I Mac guy, so I don’t know exactly where it is). It would be interesting to see if the IP address changes as you move from location to location - I bet it doesn’t.
Thank you for the clarification. Is that what “static” IP address means?
So this means that my cable company–for example–has a unique IP address for each customer, right? That is, the cable that goes from the their trunk line on the street to my house has a unique identifier that never changes? And that if you really want to identify where something comes from on the internet from the outside, the best you can do is identify, for example, that line which enters the customer’s property. From that point, only the private LAN knows who is who? And that even then, those addresses are usually “dynamic” anyway, meaning that they are just arbitrary addresses assigned every time a machine connects to the LAN? If someone walked into a public library and used the library’s wireless network to send a threat to the president, for example, using a webmail address created for only that purpose, the only real identification that could be made would be the library? Beyond that, you wouldn’t know who did it?
(Thanks also.) Not to hijack, but don’t you think that if they had known how the full range of networking was going to pan out, they would have chosen a different, perhaps simpler, more straightforward protocol system from the start? It seems to me that once wireless communication came onto the horizon with personal computers, they had to scramble to create a new addressing systems that suddenly became very susceptible to all kinds of compatibility issues.
This is an example of the last comment in my post directly above. Why would they want to do this?
Or, more to the point, why do they have so many different ways for wireless LANs to be configured, so that it seems like there are ever more possibilities for things to go wrong, or for one device to be useless with other devices?
Well, in the case of the device I’m thinking of (a Multitech GSM modem), it doing this has the advantage of eliminating a lot of possible malware and D.O.S. attacks. It means that only customers who have assess to the tunnel can directly talk to the modem.
First of all, an increased number of available addresses makes things more complicated, not simpler. Routing is now a more difficult problem, and the addresses are significantly longer.
I think you have to realize that at the time, 4 billion addresses sounded like rather a lot. Try telling someone at the time that we’d someday use that many addresses at once, and you’d get laughed out of the room. Another thing to consider is the “human consumability” of IPv4 addresses, vs IPv6. If you have to remember 192.168.1.2, that’s pretty easy. With IPv6 you will have to remember 2001:0db8:85a3:0000:0000:8a2e:0370:7334. Good luck!
Finally, I should point out that in the very early days of the development of internet technology, the whole notion of a worldwide packet switched network like we have now was not taken seriously by the telephone companies. There was resistance (in favor of direct circuit systems) for some time. It’s not at all fair to assume that what has transpired should have been obvious - you can say that now with the benefit of hindsight.
Well, not necessarily. If your cable modem uses DHCP, it may ask the cable company for a new IP address each time you turn it on. Sometimes the cable company will always assign the same one, sometimes it may assign whatever’s available. Some cable companies don’t use DHCP and have the same IP address assigned to the same modem at all times.
Even if you have a dynamic IP address, the cable company will have logs of who had what IP address at what time, so if you’re trying to track down some nefarious activity and you knew exactly what time it occurred, you could do it that way.
If I have a cable company or phone company internet provider, does my IP address change constantly or is it usually the same?
Does my cable company IP address reveal the region of the country I’m in?
If a website bans an IP address, is this actually effective if the bannee has a regular cable or phone company service provider?
ETA: Oops, I didn’t see friedo’s reply when I posted. I guess the answer is that it depends?
It depends on the company.
Yes, for a variable definition of “region.”
It depends on whether the address is dynamic. A website operator can easily ban a whole range of addresses assigned to a given ISP, though.
In 1974 4 (and a bit) billion seemed like loads! Oh well, the next level IPv6 is handy enough unless we end up having a universe-sized empire.
We’re definitely going to need IPv7 once we start networking all the other planes of existence together.
I’m not at all saying they should have known. I’m just hypothesizing if they somehow could have known, they would have chosen a different way, and been able to do it. In fact, I’m kind of amazed that networking works as well as it does, considering how much has changed since the days of putting a telephone handset into a cradle so it could connect a terminal with a mainframe on the other side of town.
You also have to remember this was back in the mists of time when computers had 128K bytes of memory or less. Extra address bits cost a lot more than they do now.