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I have seen LAN IP addresses in the following ways:

10.0.0.*

192.168.0.*

192.168.1.*

192.168.2.*

127.0.0.* (This one is normally with a 1, and I'm not sure if it is LAN, since I see it normally with proxy stuff.)

So, why are there different forms of an LAN IP addresses, and what do they mean/represent?

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up vote 25 down vote accepted

There are many questions which deal with this but here is a crash course on what are called 'Private IP Addresses' as defined in RFC 1918

IP addresses were broken up in to what are called classes as seen here, this is no longer used (replaced with CIDR) but may help to understand different sizes of networks:

IP Address Map - source: http://mreze.vigimnazija.edu.rs/wp-content/uploads/2014/02/ip-class.jpg

There are a couple basic distinctions regarding addresses. You have what are called "Networks", "Network Addresses", "Public Addresses", "Private Addresses", and "Subnets"

In short, your computer gets and IP address which resides in a particular IP network, your computers IP address and your network's address (usually defined in your local router) are 'Private addresses'. Private addresses differ from Public addresses in that private address are not assigned to public networks. For instance, if you ping 'google.com' you will receive a response from the public address which google.com resolves to. That is a public address. There are some networks which are 'special' and do not get assigned publicly, they are called Private IP addresses. For more, read here: http://whatismyipaddress.com/private-ip

Here are a list of the private network ranges:

> 192.168.0.0 - 192.168.255.255 (65,536 IP addresses)
> 172.16.0.0 - 172.31.255.255 (1,048,576 IP addresses)
> 169.254.0.0 - 169.254.255.255 (65,536 IP addresses)
> 10.0.0.0 - 10.255.255.255 (16,777,216 IP addresses)

The easiest way, I think, to visualize this is to imagine the following. Your internet provider gives you a single IP address. Let's call it 50.100.101.154. This is plugged in to your modem/router of your home. That is the public interface's IP address. However, you have more than on device you want on your network, so what your modem/router does is it creates an 'internal' network. Let's say it picks the number 192.168.1.0 for the network and it's a standard netmask (read related links to find out more). This means that you can plug in devices inside of your router and give them any IP address which fits in this pattern: 192.168.1.1-254. The last octect (space after the last period) is your 'available range' of host IP addresses. There are some special IP addresses (network address, broadcast address, etc.) but, if you don't use a 0 or a 255, you'll be fine in most cases.

So, the short answer is, 10.x.x.x, 192.168.x.x, 172.16-31.x.x are all IP addresses which you can use in your own home network which will never conflict with public IP addresses. This is important for the following reason:

When you try to go to a website, say google.com, and your browser goes to the DNS servers on the internet and says 'Where is google.com?' it gets a response back in the form of an IP address. The response is basically, "If you want to get to google.com, go to 8.8.8.8" So your browser then sends a request to 8.8.8.8 and loads whatever page is there.

So, what if you used 8.8.8.8 for an IP address in your network? Well, you might have an issue because your router may say "I know where 8.8.8.8 is, it's right over there!' and then you end up losing access to google.com because you can't get out of your network and resolve the correct 8.8.8.8 address. Since private IP address ranges are designated for private use public websites should never be using them and therefore you shouldn't ever lookup a website address (outside of your LAN) which points to one of them.

127.0.0.1 is a special type of address called your 'localhost' address and I won't go in to it here. It does cover the whole 127 range: 127.0.0.0 - 127.255.255.255 Think of it as a way to give a device it's own IP address without anyone or anything else being able to do stuff with that address.

Let me know if you have further questions!

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Well, I use the American Method, I love an easy solution for any hard problem or argument, then i can tell you basically this:

Private IPs Class:

Class A: 10.0.0.0 to 10.255.255.255 Class B: 172.16.0.0 to 172.31.255.255 and 127.0.0.* Class C: 192.168.0.0 to 192.168.255.255

Class A: for big Networks (International Companies) Class B: is used for medium-sized networks . A good example is a large college campus. Class C: The class C addresses are commonly used for small to medium sized businesses.

Broadcast - messages that target all computers on a network are sent as broadcast . These messages always use the IP address 255.255.255.255

An IP address is a numerical label that identifies a logical and hierarchical manner , to an interface ( communication element / connection) of a device (usually a computer ) within a network using IP (Internet Protocol) , which corresponds network -level TCP / IP protocol.

Private IP address : to be identified within the local network ( intranet) , Public IP address : to identify within the external network (extranet ) .

Cesar Caracas 2016 &#<>Jan

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1  
Misleading, as class B historically meant a /16 such as 192.168.0.0/16 and class C meant a /24. There was no class for a /12 such as 172.16.0.0/12, – MSalters Jan 20 at 8:52

IP addresses are 32-bit binary numbers. To make them easier to read by humans, we divide the 32 bit number into 8-bit groups, convert each gruop into decimal, them put periods between them to separate them.

So:

11000000101010000000001000000001 
becomes
11000000 10101000 00000010 00000001
becomes
192      168        2          1
and is written
192.168.2.1

All IP addresses are formed this way. There's no special thing as a LAN address.

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There are other "special kinds" of addresses – loopback and multicast are usually treated differently by the OS, for example. – grawity Jan 20 at 6:27
2  
There is such a thing as a LAN address, and that is any address reachable without going through a gateway. But you can't derive this from just an IP address, you also need your own address and your address mask. – MSalters Jan 20 at 8:49
1  
IP addresses may also be 128-bit binary numbers – Lưu Vĩnh Phúc Jan 20 at 10:18
    
@LưuVĩnhPhúcthe OP was speaking of IPv4 addresses. – Ron Trunk Jan 20 at 11:03
    
@MSaltersThe same is true for any IP address. WAN addresses or point to point links still have gateways. A worldwide L2 network fits your definition of LAN. – Ron Trunk Jan 20 at 11:07

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