what do u meant by Public IP & Private IP and Difference in between it?/?

Question

what do u meant by Public IP & Private IP and Difference in between it?/

Answer 1

Public Addresses

If you want direct (routed) connectivity to the Internet, then you must use public addresses. If you want indirect (proxied or translated) connectivity to the Internet, you can use either public or private addresses. If your intranet is not connected to the Internet in any way, you can use any unicast IPv4 addresses that you want. However, you should use private addresses to avoid network renumbering if your intranet ever directly connects to the Internet.

ICANN assigns public addresses, which consist of either historically allocated classful address prefixes or, more recently, CIDR-based address prefixes that are guaranteed to be unique on the Internet. For CIDR-based address prefixes, the value of w (the first octet) ranges from 1 to 126 and from 128 to 223, with the exception of the private address prefixes described in the "Private Addresses" section of this chapter.

When ICANN assigns a public address prefix to an organization, routes are added to the routers of the Internet so that traffic matching the address prefix can reach the organization. For example, when an organization is assigned an address prefix, that address prefix also exists as a route in the routers of the Internet. IPv4 packets that are sent to an address within the assigned address prefix are routed to the proper destination.
Illegal Addresses

Private organization intranets that do not need an Internet connection can choose any address scheme they want, even using public address prefixes that ICANN has assigned to other networks. If the private organization later decides to directly connect to the Internet, these addresses could conflict with existing public addresses and become illegal addresses. Organizations with illegal addresses cannot receive traffic at those addresses because the routers of the Internet send traffic destined to ICANN-allocated address prefixes to the assigned organizations, not to the organizations using illegal addresses.

For example, a private organization chooses to use the 206.73.118.0/24 address prefix for its intranet. ICANN has assigned that prefix to the Microsoft Corporation, and routes exist on the Internet routers to send all packets for IPv4 addresses on 206.73.118.0/24 to Microsoft. As long as the private organization does not connect to the Internet, it has no problem because the two address prefixes are on separate IPv4 networks; therefore, the addresses are unique to each network. If the private organization later connects directly to the Internet and continues to use the 206.73.118.0/24 address prefix, any traffic sent through the Internet to those addresses will arrive at Microsoft, not the private organization.
Private Addresses

Each IPv4 interface requires an IPv4 address that is unique within the IPv4 network. In the case of the Internet, each IPv4 interface on a subnet connected to the Internet requires an IPv4 address that is unique within the Internet. As the Internet grew, organizations connecting to it required a public address for each interface on their intranets. This requirement placed a huge demand on the pool of available public addresses.

When analyzing the addressing needs of organizations, the designers of the Internet noted that, for many organizations, most of the hosts did not require direct connectivity to the Internet. Those hosts that did require a specific set of Internet services, such as Web access and e-mail, typically accessed the Internet services through Application layer gateways, such as proxy servers and e-mail servers. The result is that most organizations required only a few public addresses for those nodes (such as proxies, servers, routers, firewalls, and translators) that were directly connected to the Internet.

Hosts within the organization that do not require direct access to the Internet required IPv4 addresses that do not duplicate already-assigned public addresses. To solve this addressing problem, the Internet designers reserved a portion of the IPv4 address space for private addresses. IPv4 addresses in the private address space are known as private addresses and never assigned as public addresses. Because the public and private address spaces do not overlap, private addresses never duplicate public addresses.

RFC 1918 defines the following address prefixes for the private address space:
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10.0.0.0/8 (10.0.0.0, 255.0.0.0)

Allows the following range of valid IPv4 unicast addresses: 10.0.0.1 to 10.255.255.254. The 10.0.0.0/8 address prefix has 24 host bits that you can use for any addressing scheme within a private organization.
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172.16.0.0/12 (172.16.0.0, 255.240.0.0)

Allows the following range of valid IPv4 unicast addresses: 172.16.0.1 to 172.31.255.254. The 172.16.0.0/12 address prefix has 20 host bits that you can use for any addressing scheme within a private organization.
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192.168.0.0/16 (192.168.0.0, 255.255.0.0)

Allows the following range of valid IPv4 unicast addresses: 192.168.0.1 to 192.168.255.254. The 192.168.0.0/16 address prefix has 16 host bits that you can use for any addressing scheme within a private organization.

Because ICANN will never assign the IPv4 addresses in the private address space to an organization connected to the Internet, Internet routers will never contain routes to private addresses. You cannot connect to a private address over the Internet. Therefore, a host that has a private address must send its Internet traffic requests to an Application layer gateway (such as a proxy server) that has a valid public address or through a network address translation (NAT) device that translates the private address into a valid public address.

Answer 2

Because every thing on the Internet needs an IP address, and there is only a set number of IP address available, we do not have enough to go around. So some smart people have come up with the idea of public and private ip addresses.

A public IP is an IP address that can be seen on the Internet and is rout-able(if this is a word). These ip address are usually assigned to routers. When you go to places like yahoo.com you are actually using a public IP.

A private IP is used on a private network such as your home or company network. These private ip address can not be seen on the internet. Now I am sure you are asking if they can not be seen on the internet, then how can we surf the internet with them.
There is something on a network called NAT (Network Address Translation) which basically maps a private IP address to a public. You can map as many private IP's to a single public ip as you like, but really this is depending on bandwidth.

Answer 3

Private IPs are used in local area networks only (LAN). These type of IPs are not allowed to be used in the internet. If you are using a private IP address and you would like to connect to the internet, you would need a device that would translate this private IPs into Public IP such as a Network Address Translator (NAT).

Public IPs are the standard IPs that are allowed to be used in the internet. These IPs are unique world wide unlike Private IPs, which are unique locally only.

The reason why these IPs are segregated is to give the standards which IPs to use locally and which IPs to use when a network is going to be connected to a bigger network, the Internet.

Answer 4

I want to give you a simple example. Suppose you have a LAN. There are 5 pieces of computers. Their IP addresses are:
192.168.1.11,
192.168.1.12,
192.168.1.13,
192.168.1.14 &
192.168.1.15
All of them are interconnected. Now you want to use Internet in all the computers. Then you have to take a broadband line (suppose) from an ISP. The ISP will give you a device (router or gateway or something like this device) that contains an IP address like:
202.191.120.4
This IP address is public or real. This is a unique one in the world. The above device will be able to contain another IP like:
192.168.1.1
This IP will be used as a gateway for your LAN. All the requests for Internet from your LAN will be forwarded via 192.168.1.1 to 202.191.120.4 to Internet. Means requests forwarded via private IP to public IP.

So, Private IP may be duplicate but Public IP will never be duplicate.

Answer 5

public IPs are IP addresses everyone can see. Private IPs are IPs used in a local network and are all behind the firewall. They are not exposed to the internet (public).

Answer 6

public ip means every 1 can c it
private ip need 2 password 2 c it

Answer 7

http://www.wisegeek.com/what-is-the-difference-between-public-and-private-ip-addresses.htm