Explanation of IP Address



A brief explanation of IPs and how they are affected by Broadband, Routers and Contention Ratios, plus a comparison of IPv4 and IPv6


What is an IP ?
An IP is a slang term for the numerical address of a computer or resource on a network. The initials stand for Internet Protocol, and the correct term in full is 'IP address'.

Any network has IPs, and that includes the largest - the Internet - and the smallest: your PC and router. In fact even your own PC has a local network within itself, with a local IP for the PC itself, so that it can route traffic correctly if you have a server application of some sort installed and then query it from within the same PC (it's This IP is also used on a server for its own local traffic, for example to/from MySQL databases.

A server is just an ordinary PC, usually running Linux instead of Windows, usually 64-bit, with more RAM than usual (8GB is a common figure though some go to 32GB), fast disks, and not much in the way of graphics capability.

Broadband IPs
Most people want to know about their broadband IP. On DSL (DSL equals ADSL equals broadband), all IPs are dynamic. The word dynamic means changing / moving / unconstant. DSL IPs are never static (stable /unmoving / the same).

The broadband provider, the ISP, changes your IP as needed. Some change customers' IPs daily at 5am for example, others change them after a variable period of time. The only constant is that they will change. There are two main reasons: contention ratio and hosting restrictions.

ADSL by the way stands for asymmetric digital subscriber line, indicating that the up and down speed are different. On the lowest speed of DSL, which is 512kB or 'half-megabyte' broadband, the download speed is 512kB and the upload speed is often 60kB. On 1,024kB or one-megabyte DSL, down / up speeds are normally 1MB and 120kB. Up to 24MB DSL is available in many cities, with even faster speeds in some areas.

SDSL stands for symmetric DSL, which is 'business broadband'. IPs are static, since a business may need to host services, and so they pay more for the facility. Contention ratios are much better (but still in effect).

The reason that a static IP is needed for the hosting of services is because the numerical IP is your address on the Internet, and that address needs to stay contant or people cannot find you. There are two common exceptions to this, but nevertheless a static IP is preferable for some hosted services.

Domain names
One exception to the need for a constant, static IP is the DNS or domain name service. People prefer human-readable names, not numbers, and therefore locate their resources at example.com and not, because humans have analog-based memory systems, not digital, and cannot remember a series of numbers reliably. But a network cannot function with 100 million-plus addresses with human-style names, so numbers are used in order to create an efficient digital address system. The problem then becomes how to equate one with the other, especially as the equivalents are constantly changing. You want to go to example.com, but its actual global address is or similar. The answer is the DNS system, which tells you (in practice your browser) where example.com is actually located digitally. The central servers know what real address the human-readable name is at, and where exactly that digital address is physically located, and the route you need to go to get there. Your browser gets this information in a fraction of a second every time you go to a new website that you haven't visited recently - and the speed and efficiency of DNS is one of the wonders of the web.

The other common exception to a static IP always being needed for hosting on the web is that you can now sign up to a DynamicDNS service, which automatically finds the current IP for your site my-example.com and tells the web where you are. Good domain registrars provide this for free.

This means that even when your ISP changes your IP, as they will sooner or later, others can still find your hosted services. ISPs don't like you hosting services, though, on what is essentially cheap broadband, because it means you will be uploading much more than the average customer - and upload capacity costs them far more than download bandwidth. This is one of the main reasons they try and restrict your ability to host services such as websites and data storage on their consumer DSL service - they prefer you to pay extra for their business plan.

Contention ratio
This is the ratio of actual network equipment capacity at the ISP to the number of customers. There is never enough equipment to physically supply network services at full speed to all the subscribers, as it is not economic to have such a capability since most customers will not be using the service fully at any given time. Therefore equipment is switched around as necessary to support subscribers as they utilise more of the service. The ratio of customers to equipment is commonly 50:1 (spoken as 'fifty to one') although on a premium service it may be as low as 20:1, perhaps even 10:1 if you pay enough.

On dial-up Internet, which is still used by rural and coastal customers as there is no plant (cabled supply) for many such customers yet even in the smallest and most highly-industrialised countries, the contention ratio is worse and can be as high as 100:1, which is another reason dial-up Internet is so poor.

With dial-up it may be the case that modems are switched in or out for customers so that in some cases they will not be able to receive any service at all, but on a broadband service the effect of the contention ratio is simply that at peak times there is less bandwidth, so speeds are lower. In other words you may pay for 2MB broadband (which is the full theoretical download speed of that deal) but at peak times you might only get 1MB download speed.

Cable TV IPs
With cable TV / telephone / Internet service, the connection is still DSL although there are some differences to phone line DSL. Firstly, the IPs are still dynamic, but called sticky IPs. This is because they change far less often than phone DSL IPs, as the contention ratio is better (although still in effect). It means that an IP can last for months before it is changed. The bandwidth is potentially better for all customers as well, since the service comes into the building on a coaxial cable, which has much higher bandwidth than the small phone line twisted-pair cable.

This is also why modems and routers are different for cable or phone DSL. A phone line DSL service needs just one box for the router (the part that supplies the service to different PCs around the building) and the modem (the part that communicates with the outside world), as the connection is a phone jack. The two distinct functions of modem and router are combined in one box.

A cable TV-based service however needs two boxes, a modem that connects to the street cable, which is 'coax' (the same class of cable that goes to your satellite or TV aerial), and is owned by the cable company since they specify it and set it up; and a separate router that supplies the service around the building, and that you own. You can't swap a phone and cable 'router' for this reason.

How to get a new IP
An Internet IP is assigned to you by your ISP (Internet service provider). As we have seen, this number can change. You can find your IP by many different methods but the easiest is probably just to go to a website that tells you - search 'find your ip' to locate these websites.

On phone broadband you can get a new IP by rebooting your router. This can be done by accessing the router management and choosing disconnect, then reconnect; or by a software reboot. If you don't know how to access your router on the network, just switch it off, wait ten seconds, then switch it on again.

A cable router is a different prospect because you may not be able to get a new IP even by rebooting, since IPs are sticky - they change when they expire. You can try switching off both router and modem for two hours and then reconnecting, although occasionally a shorter power down may work. When reconnecting, first switch on the modem and leave for two minutes. Then switch on the router, and you should be back up.

With a dial-up modem, every time you connect, you get a new IP.

On ISDN, which was an intermediate technology used between the eras of dial-up and broadband, you cannot disconnect the terminal box for more than 15 minutes or the service shuts off. ISDN can still be used where the only option is dial-up, as it works at extended distance from the telephone exchange, unlike DSL. The max speed is 125kB and although this is just a fraction of the slowest broadband speed, it's still a lot faster than dial-up, which although theoretically is 7kB, is more likely to be 5 or 6kB in practice. And where the phone company digitally splits the service to two subscribers, as they often do when there is a plant shortage (not enough street cable) - and usually without telling the subscribers - then speed is halved. This is called a DACS splitter.

ISPs with one IP for all customers
If you want to get a new web IP for some reason, you can normally just reboot your router to achieve this. But in some cases this won't be possible, and you are stuck: there are some ISPs who issue the same IP to all customers, since this prevents them from hosting any kind of service. AOL and Hughes.net are examples - all their customers have the same IP on the web. Obviously, their IPs are different all the way into the ISP's equipment, otherwise they could not be differentiated on the network - but to the outside world, all customers are at one address.

It's fair to say that this arrangement sucks, if you are anything other than a very basic home user. On the other hand, this is what you have paid for, and is therefore the deal you signed up to. To get a new web IP you would need to use a proxy server, though this is only of use for browsing, and cannot help if you need to transfer files directly to another PC using on-PC FTP servers at each end such as the Core Micro-FTP server, or via a mini HTTP server such as HFS. In these cases you are obviously not a basic home user, and should sign up for a real broadband service. Hughes.net customers though might be restricted by the fact this is a radio service and therefore specifically for remote dwellers.

Your PC's IP
Every PC has a 'local IP' - an address used within the machine itself, which is normally - but this is only used for traffic within the PC. For example if you have a server application like XAMPP installed on it, because you only have one PC and want to use that as both server and client, perhaps to build websites with. This works but is not optimal, server software work ideally needs two PCs.

Your network IPs
On your home or office network, the IPs are set by your own router. Even if connected to the Internet, that would have no effect on your network IPs - the ISP for example cannot influence your own network IPs.

Common IP ranges that are employed by routers, in order of likelihood, include: 

  • through to (or higher)
  • through to (or higher)
  • through to (or higher)

Your router docs will tell you which apply to you. Alternatively, access the router control panel via your browser, and look it up in there. Routers (ie the modem router that connects you to the Internet and supplies the service to the other PCs in your home or office) all have a remote-accessible management panel; switches and hubs (simple jack boxes with more sockets to extend a network) don't. If you are connected via a hub to your router, the hub will be transparent and you'll just see the router control panel when you access it via the correct IP.

How to connect to your router control panel
To connect to your router, or indeed to any other device on the network -like the other PCs - you need to know their IP on the network. PCs can interconnect without your intervention because they have software to do this, but to get into your router control panel you'll need to know its IP.

Even when you have no idea what it is, it's easy to find:
1. Using the IPs given above, run through the most likely candidates.
2. Search the web for 'belkin router ip' or whatever your router model is.

So first you can try the likely IPs. Start with, then, then -- these cover more than 95% of routers. Enter those numbers directly into your browser address bar and hit Enter. A browser is an application that travels a network and retrieves information for you, so that's what's needed to get into your router.

If no luck, then search the web for your router IP. It would be rare not to be able to get it this way, but there are exceptions of course. For example if you have a USB LAN cable to link two PCs, perhaps where no router was available, then the IP range is likely to be unusual. Here is the starting IP number for a GeneLink USB PC-to-PC cable: -- a little hard to guess that one!

Access the router control panel
OK, you've found your router on the network and you are looking at its login page. How to get in?

It looks as if you've never been here before, so the user and password will be still on the default values. Try these two first:
1. User: leave blank. Pass: admin.
2. User: admin. Pass: admin.

This covers many routers - perhaps 75% or more. If you can't get in, you have two options:
1. Search the web for 'belkin router password' or similar.
2. Do a hard reset, to return the router to default values, maybe if you bought the router secondhand or otherwise lost the password.

Routers can be rebooted at three levels, in general. These can be used progressively, to reset the minimum amount of data to accomplish whatever job you are doing. The sequence is:

1. A reboot: this scrubs the web IP and little else. Power down - wait 10 seconds - power up.

2. A soft reset: this will scrub the net parameters and possibly the router password; you will need to re-enter all your ISP's connection details including the ISP password. Power down - disconnect from the power source - hold in the reset button for 10 seconds - power up. The reset button is similar to that found on many laptops, a 'secret' button to disconnect power and internal battery: there will be a tiny hole in the case, you insert a small probe such as a pencil tip and hold down the microswitch inside.

3. A hard reset: scrubs everything and you start from scratch. All settings are returned to default, including passwords. Power down - disconnect from the power source - hold in the reset button for 10 seconds - release the reset button - hold in the reset button again, and keep held in -reconnect the power lead - power up - release reset button after 30 seconds.

Now you are back on the default user and password, and should be able to login. Go through the different pages in the control panel and reset all your user data.

Use your own DNS IPs
While in here you can set up your own IPs for the DNS service, which is a better way of doing it than using your ISP's DNS IPs. These are the addresses that your browser goes to in order to find web resources.

The problem is that your ISP's information is typically between 12 hours and 3 days out of date, which affects your browsing speed; plus the route they set you on will use their own and their partner's networks instead of the fastest possible route; plus whenever the address is faulty in some way, they will serve you adverts; plus they build up a personal profile on you based on your DNS queries, which allows them and their partners to serve you personalised adverts. Essentially, this is a bad deal for you, and you can use an alternative DNS service to advantage.

Find the DNS IPs in the router control panel. There will be three entries, of which two will probably be filled with an IP. Replace the two entries and fill the third as well, like this:

These IPs use the OpenDNS service, which is one of the many free DNS services out there. They don't serve you ads, but instead give you helpful hints when you enter the wrong URL. The global network routes they put you on are usually faster than your ISP's version. Most important of all, for some users, will be the fact that their DNS data is updated in real time, and correct to less than 15 minutes in most cases and less than a minute sometimes - this is very important for webmasters moving sites between hosts.

There are many alternative DNS services now, so you can search for alternatives should you wish to. All have some negatives since there is no free lunch, but OpenDNS is a good starting point.

IPv4 and IPv6
In the beginning, nobody had any idea that the Internet would become the world's most important international resource, or that there would be billions of users. That there would be more than 100 million websites by 2010 was inconceivable. Because of this, the numerical address system was too simple and therefore too limited in capacity - there just weren't enough numbers available. The current system, called IPv4, is fast running out of numbers, and a new system needs implementing. This has already been implemented in fact, but as yet its impact is low since there are few users who have consumer-level visibility.

There are about 4 billion addresses available on the current system, but although it sounds a lot, there are two problems here and one pertinent fact:

  • 1. All the unused addresses are not available to be freely allocated, due to the block allocation system, which means that numbers of addresses in blocks are allocated to large-scale users and cannot be retrieved.
  • 2. In any case, the total capacity would be exceeded at some stage even if 100% allocation efficiency was possible. That point is variously estimated as being anywhere from 2011 to 2020.
  • 3. In the final analysis, the system fails when individual consumers cannot freely obtain an IP. That is already the case and therefore practical system capacity has already been reached.

Here is an example of an IPv4 address (the current / old system), and an IPv6 address - the new system:

  • an IPv4 address:
  • an IPv6 address: 1009:0db8:85a3:08d3:1319:8a2e:0370:8459

How many IPs are there in IPv6 ?
The number of potential IPv6 addresses is so large that it cannot even be expressed sensibly in words, only in mathematical terms. However, because people keep asking this question, here it is:

(1) In figures: 340,282,366,920,938,463,463,374,607,431,768,211,456

(2) In words: Three hundred and forty undecillion, two hundred and eighty-two decillion, three hundred and sixty-six nonillion, nine hundred and twenty octillion, nine hundred and thirty-eight septillion, four hundred and sixty-three sextillion, four hundred and sixty-three quintillion, three hundred and seventy-four quadrillion, six hundred and seven trillion, four hundred and thirty-one billion, seven hundred and sixty-eight million, two hundred and eleven thousand, four hundred and fifty-six.
(Rob Elamb)

(3) Or alternatively, a quote: "So we could assign an IPv6 address to every atom on the surface of the earth, and still have enough addresses left to do another 100+ earths. It isn’t remotely likely that we’ll run out of IPv6 addresses at any time in the future."
(Steve Leibson)

(4) Or as a realist would say of course, "Give it another 30 years and we'll be scratching our heads again, pal - the one thing humans are proven unable to remotely comprehend is the future".
(chris.p, 2010)


We hope this brief guide to the world of IPs was of use to you. It can always be improved of course, so please feel free to suggest corrections, improvements and updates in the Comments here, or in the Forum: on the Internet board.


This guide to IPs is maintained by volunteer editor chris.p. In the computing area his interests include freeware / open-source software, website software, and web usability for all. He is a web business manager. Registered site visitors can get in touch by clicking here.

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