Beginner's Guide to Internet Protocol (IP) Addresses

Internet Protocol (IP) addresses are the unique identifying numbers that all computers and devices connected to the Internet depend on to communicate with each other. When the pool of available unallocated addresses for IPv4, the original IP addressing system, completely depleted this year, the Internet began a transition to IPv6, a newer Internet Protocol system. This highly readable guide, created in cooperation with ICANN's At-Large community, helps the individual user understand IP addresses and the transition from IPv4 to IPv6.

English [PDF, 1.36 MB]

Beginner's Guide to Domain Names

A domain name can become where other people find you on line, and adds to your online identity. Although domain names are a big part of the Internet, understanding how these names work (and the ins and outs of obtaining them) can be mystifying at first. This highly readable guide, created in cooperation with ICANN's At-Large community, helps the individual user understand and use domain names.

If your computer is assigned a private address, but you can still access services over the Internet, then your computer is probably behind a Network Address Translator (NAT), which lets lots of computers share a single unique IP address

There are approximately 3.7 billion addresses available for ordinary Internet connections, and about 1.6 billion people used the Internet in 2009. So, very roughly, each user requires a little over two unique addresses

IP addresses are actually just long strings of numbers, like 3221226037, but to make it easier for people to read them, we write them down in a special way. IPv4 addresses are written as a string of four numbers between 0 and 255, separated by dots. A typical IPv4 address looks like this:

WhAT I S I Pv4’S hI STORy?

IPv4 has just over four billion unique IP addresses. It was developed in the early 1980s and served the global Internet community for more than three decades. But IPv4 is a finite space, and after years of rapid Internet expansion, its pool of available unallocated addresses has been fully allocated to Internet services providers (ISPs) and users.

Only 3.7 billion IPv4 addresses are usable by ordinary Internet access devices. The others are used for special protocols, like IP Multicasting. Almost three and a half billion addresses was enough for the experiment that the Internet started as in the 1980s, but it is not enough for a production network in today’s world, with its population of almost seven billion people

WhAT I S I Pv6’S hI STORy?

Standardized in 1996, IPv6 was developed as the next-generation Internet Protocol. One of its main goals was to massively increase the number of IP addresses available. The first production allocations were made to ISPs and other network operators in 1999, and by June 2006, IPv6 was successful enough that important test networks shut down. They were no longer needed.

Over the past year, major content providers and access networks have started offering IPv6 services to ordinary Internet users. Because IPv6 is so much larger than IPv4, it should last us considerably longer than the 30 years IPv4 has given us so far. But just how large is IPv6?

IPv6 is significantly bigger than IPv4. Compared to IPv4’s 32-bit address space of four billion addresses, IPv6 has a 128-bit address space, which is 340 undecillion addresses. That’s not a number you hear every day! Using IPv6, ISPs generally assign many thousands of network segments, called a /64, to a single subscriber connection used in places such as a home, classroom, or business. Giving every person on Earth a connection with a /64 would barely dent the available IPv6 address space. In fact, while the Earth’s orbit around the Sun is only big enough to contain 3,262 Earths put side by side, it would take 21,587,961,064,546 Earths to use all the addresses in the part of the IPv6 space we now use.

New gTLD application period begins


The New gTLD application period opened as planned on January 12th. This step to allow organizations to apply for their own top level domain names comes after six years of policy development that involved multiple stakeholder input from the broad internet community.

Speaking at the Center for Strategic & International Studies in Washington DC two days before the opening of the application period, ICANN president Rod Beckstrom referred to the new gTLD program as “the most significant opening in the history of the domain name system”. He also noted that during the six years leading up to the application period over 2,000 comments were received regarding the program and proposed guidelines which contributed to the current version of the Applicant Guidebook.

The gTLD program has drawn intense criticism from the corporate community over ongoing concerns of increasing costs to defend against trademark abuse. US corporations and organizations have been most outspoken in voicing these concerns, but not alone. A number of intergovernmental organizations have expressed concern about the cost of applying and perceptions about the increased opportunity for Internet fraud.

Following two US Government hearings in December ICANN was asked by the US Federal Trade Commission to “mitigate the risk of serious consumer injury and to improve the accuracy of Whois data” before approving any new gTLD applications. The written response from ICANN stated “ICANN’s multi-stakeholder community will continue to work on issues identified by the FTC and others to enhance the security and stability of the DNS.” and went on to describe the ongoing commitments to address the FTC’s concerns.

While the process has been contentious, estimates regarding the number of gTLDs has expanded significantly over the past year. With a few exceptions, potential applicants have been keeping their intentions private, but the range of 1,000 – 1,500 applications appears to be the range most often quoted. Melbourne IT has spoken with many organizations to assist them in the decision making process of whether to apply or not apply, and is assisting over 100 organizations with their applications.

“The new address structures will test which companies see the Internet as the main way to reach customers” is how Theo Hnarakis, Melbourne IT’s chief executive sees new gTLDs. Cybersquatting isn’t an issue for top level domains so the decision is all about the brand and improving customer interaction. Many of the possibilities that apply from a brand utilization standpoint aren’t possible within the current naming structure and will have to be developed. This will impact SEO and potentially even website architecture. A gTLD isn’t for everyone. Each company has to look at their brand and marketing efforts and decide what’s in their best strategic interest.

For organizations that haven’t finalized a decision whether to apply or not, there’s not a lot of time left. Applicants will need to register in ICANN’s top level domain application system (TAS) by March 29th to reserve their application slot. The gTLD application itself will need to be filed prior to April 12, 2012

Making IPv6 the New Normal

A year ago today ICANN allocated the last five IPv4 address blocks to the five Regional Internet Registries in a ceremony with leaders from the Internet Architecture Board and the Internet Society. The use of the next generation of Internet addressing – IPv6 – has been steadily growing in that year and that's a good thing, because IPv6 is how the Internet will continue to serve as a platform for innovation and economic development.

IPv6 vastly increases the number of available Internet addresses. The architecture of IPv4 allowed for four billion Internet addresses. That's no longer sufficient on a planet of 7 billion humans, where many of those humans have multiple devices attached to the Internet. Every device connected to the Internet needs an IP address, whether it is a smartphone, mail server, laptop or web server.

Almost 6,700 IPv6 networks were publicly routed on the Internet in January 2012, and more are expected in the months leading up to World IPv6 Launchon 6 June 2012. On that day, Internet service providers, web companies and home networking equipment manufacturers around the world are asked to permanently enable IPv6.

ICANN Seeks Evaluators for the Support Applicant Review Panel (SARP) - Request for Expressions of Interest (EOI)

3 February 2012

ICANN is seeking individuals to serve on the Support Applicant Review Panel (SARP), an important component of the New gTLD Applicant Support Program that seeks to serve the global public interest by ensuring worldwide accessibility to, and competition within, the New gTLD Program. Panelists will be responsible for evaluating and scoring applications for financial assistance.

As new gTLDs are ushering in the biggest change to the Internet in years, SARP volunteers will be on the front line of the effort to lessen the digital divide by expanding the Internet to less-developed parts of the world. They will be part of an exclusive group of individuals chosen for their background and experience in areas such as running a small business, operating in developing economies, analyzing business plans, serving in the public interest, managing a domain name registry service, or awarding grants. SARP volunteers will make a real and lasting contribution to ensuring that the opportunities for innovation and economic development created by the Internet are open to all.

The financial assistance component of the Applicant Support Program offers a limited number of qualifying applicants the opportunity to pay a reduced evaluation fee of USD 47,000 instead of the full evaluation fee of USD 185,000.

SARP members will evaluate support applications against the established public interest, financial capabilities and financial need criteria outlined in the Financial Assistance Handbook [PDF, 710 KB] and as a group they will score each applicant. It is important to note that panelists will not weigh the relative merits of overall gTLD applications.

If you are interested in applying to be a SARP member, please review the criteria, time commitment and other expectations as detailed in the posted EOI [PDF, 172 KB].

Useful References


Suleras:About Suleras:Pp-semi-indefSuleras:Pp-move-indef An Internet Protocol address (IP address) is a numerical label assigned to each device (e.g., computer, printer) participating in a computer network that uses the Internet Protocol for communication.[1] An IP address serves two principal functions: host or network interface identification and location addressing. Its role has been characterized as follows: "A name indicates what we seek. An address indicates where it is. A route indicates how to get there."[2]

The designers of the Internet Protocol defined an IP address as a 32-bit number[1] and this system, known as Internet Protocol Version 4 (IPv4), is still in use today. However, due to the enormous growth of the Internet and the predicted depletion of available addresses, a new addressing system (IPv6), using 128 bits for the address, was developed in 1995,[3] standardized as RFC 2460 in 1998,[4] and its deployment has been ongoing since the mid-2000s.

IP addresses are binary numbers, but they are usually stored in text files and displayed in human-readable notations, such as (for IPv4), and 2001:db8:0:1234:0:567:8:1 (for IPv6).

The Internet Assigned Numbers Authority (IANA) manages the IP address space allocations globally and delegates five regional Internet registries (RIRs) to allocate IP address blocks to local Internet registries (Internet service providers) and other entities.

IP versionsEdit

Two versions of the Internet Protocol (IP) are in use: IP Version 4 and IP Version 6. Each version defines an IP address differently. Because of its prevalence, the generic term IP address typically still refers to the addresses defined by IPv4. The gap in version sequence between IPv4 and IPv6 resulted from the assignment of number 5 to the experimental Internet Stream Protocol in 1979, which however was never referred to as IPv5.

IPv4 addressesEdit


Talaksan:Ipv4 address.svg

In IPv4 an address consists of 32 bits which limits the address space to Suleras:Gaps (232) possible unique addresses. IPv4 reserves some addresses for special purposes such as private networks (~18 million addresses) or multicast addresses (~270 million addresses).

IPv4 addresses are canonically represented in dot-decimal notation, which consists of four decimal numbers, each ranging from 0 to 255, separated by dots, e.g., Each part represents a group of 8 bits (octet) of the address. In some cases of technical writing, IPv4 addresses may be presented in various hexadecimal, octal, or binary representations.

IPv4 subnettingEdit

In the early stages of development of the Internet Protocol,[1] network administrators interpreted an IP address in two parts: network number portion and host number portion. The highest order octet (most significant eight bits) in an address was designated as the network number and the remaining bits were called the rest field or host identifier and were used for host numbering within a network.

This early method soon proved inadequate as additional networks developed that were independent of the existing networks already designated by a network number. In 1981, the Internet addressing specification was revised with the introduction of classful network architecture.[2]

Classful network design allowed for a larger number of individual network assignments and fine-grained subnetwork design. The first three bits of the most significant octet of an IP address were defined as the class of the address. Three classes (A, B, and C) were defined for universal unicast addressing. Depending on the class derived, the network identification was based on octet boundary segments of the entire address. Each class used successively additional octets in the network identifier, thus reducing the possible number of hosts in the higher order classes (B and C). The following table gives an overview of this now obsolete system.

Historical classful network architecture
Class Leading bits in address (binary) Range of first octet (decimal) Network ID format Host ID format Number of networks Number of addresses per network
A 0 0–127 a b.c.d 27 = 128 224 = Suleras:Gaps
B 10 128–191 a.b c.d 214 = Suleras:Gaps 216 = Suleras:Gaps
C 110 192–223 a.b.c d 221 = Suleras:Gaps 28 = 256

Classful network design served its purpose in the startup stage of the Internet, but it lacked scalability in the face of the rapid expansion of the network in the 1990s. The class system of the address space was replaced with Classless Inter-Domain Routing (CIDR) in 1993. CIDR is based on variable-length subnet masking (VLSM) to allow allocation and routing based on arbitrary-length prefixes.

Today, remnants of classful network concepts function only in a limited scope as the default configuration parameters of some network software and hardware components (e.g. netmask), and in the technical jargon used in network administrators' discussions.

IPv4 private addressesEdit

Early network design, when global end-to-end connectivity was envisioned for communications with all Internet hosts, intended that IP addresses be uniquely assigned to a particular computer or device. However, it was found that this was not always necessary as private networks developed and public address space needed to be conserved.

Computers not connected to the Internet, such as factory machines that communicate only with each other via TCP/IP, need not have globally unique IP addresses. Three ranges of IPv4 addresses for private networks were reserved in RFC 1918. These addresses are not routed on the Internet and thus their use need not be coordinated with an IP address registry.

Today, when needed, such private networks typically connect to the Internet through network address translation (NAT).

IANA-reserved private IPv4 network ranges
Start End No. of addresses
24-bit block (/8 prefix, 1 × A) Suleras:Gaps
20-bit block (/12 prefix, 16 × B) Suleras:Gaps
16-bit block (/16 prefix, 256 × C) Suleras:Gaps

Any user may use any of the reserved blocks. Typically, a network administrator will divide a block into subnets; for example, many home routers automatically use a default address range of through (

IPv4 address exhaustionEdit

IPv4 address exhaustion is the decreasing supply of unallocated Internet Protocol Version 4 (IPv4) addresses available at the Internet Assigned Numbers Authority (IANA) and the regional Internet registries (RIRs) for assignment to end users and local Internet registries, such as Internet service providers. IANA's primary address pool was exhausted on February 3, 2011 when the last 5 blocks were allocated to the 5 RIRs.[5][6] APNIC was the first RIR to exhaust its regional pool on 15 April 2011, except for a small amount of address space reserved for the transition to IPv6, intended to be allocated in a restricted process[7]

IPv6 addressesEdit


Talaksan:Ipv6 address.svg

The rapid exhaustion of IPv4 address space, despite conservation techniques, prompted the Internet Engineering Task Force (IETF) to explore new technologies to expand the Internet's addressing capability. The permanent solution was deemed to be a redesign of the Internet Protocol itself. This next generation of the Internet Protocol, intended to replace IPv4 on the Internet, was eventually named Internet Protocol Version 6 (IPv6) in 1995[3][4] The address size was increased from 32 to 128 bits or 16 octets. This, even with a generous assignment of network blocks, is deemed sufficient for the foreseeable future. Mathematically, the new address space provides the potential for a maximum of 2128, or about Suleras:Val unique addresses.

The new design is not intended to provide a sufficient quantity of addresses on its own, but rather to allow efficient aggregation of subnet routing prefixes to occur at routing nodes. As a result, routing table sizes are smaller, and the smallest possible individual allocation is a subnet for 264 hosts, which is the square of the size of the entire IPv4 Internet. At these levels, actual address utilization rates will be small on any IPv6 network segment. The new design also provides the opportunity to separate the addressing infrastructure of a network segment — that is the local administration of the segment's available space — from the addressing prefix used to route external traffic for a network. IPv6 has facilities that automatically change the routing prefix of entire networks, should the global connectivity or the routing policy change, without requiring internal redesign or renumbering.

The large number of IPv6 addresses allows large blocks to be assigned for specific purposes and, where appropriate, to be aggregated for efficient routing. With a large address space, there is not the need to have complex address conservation methods as used in Classless Inter-Domain Routing (CIDR).

Many modern desktop and enterprise server operating systems include native support for the IPv6 protocol, but it is not yet widely deployed in other devices, such as home networking routers, voice over IP (VoIP) and multimedia equipment, and network peripherals.

IPv6 private addressesEdit

Just as IPv4 reserves addresses for private or internal networks, blocks of addresses are set aside in IPv6 for private addresses. In IPv6, these are referred to as unique local addresses (ULA). RFC 4193 sets aside the routing prefix fc00::/7 for this block which is divided into two /8 blocks with different implied policies The addresses include a 40-bit pseudorandom number that minimizes the risk of address collisions if sites merge or packets are misrouted.[8]

Early designs used a different block for this purpose (fec0::), dubbed site-local addresses.[9] However, the definition of what constituted sites remained unclear and the poorly defined addressing policy created ambiguities for routing. This address range specification was abandoned and must not be used in new systems.[10]

Addresses starting with fe80:, called link-local addresses, are assigned to interfaces for communication on the link only. The addresses are automatically generated by the operating system for each network interface. This provides instant and automatic network connectivity for any IPv6 host and means that if several hosts connect to a common hub or switch, they have a communication path via their link-local IPv6 address. This feature is used in the lower layers of IPv6 network administration (e.g. Neighbor Discovery Protocol).

None of the private address prefixes may be routed on the public Internet.

IP subnetworksEdit

IP networks may be divided into subnetworks in both IPv4 and IPv6. For this purpose, an IP address is logically recognized as consisting of two parts: the network prefix and the host identifier, or interface identifier (IPv6). The subnet mask or the CIDR prefix determines how the IP address is divided into network and host parts.

The term subnet mask is only used within IPv4. Both IP versions however use the Classless Inter-Domain Routing (CIDR) concept and notation. In this, the IP address is followed by a slash and the number (in decimal) of bits used for the network part, also called the routing prefix. For example, an IPv4 address and its subnet mask may be and, respectively. The CIDR notation for the same IP address and subnet is, because the first 24 bits of the IP address indicate the network and subnet.

IP address assignment Suleras:Anchor Edit

Internet Protocol addresses are assigned to a host either anew at the time of booting, or permanently by fixed configuration of its hardware or software. Persistent configuration is also known as using a static IP address. In contrast, in situations when the computer's IP address is assigned newly each time, this is known as using a dynamic IP address.


Static IP addresses are manually assigned to a computer by an administrator. The exact procedure varies according to platform. This contrasts with dynamic IP addresses, which are assigned either by the computer interface or host software itself, as in Zeroconf, or assigned by a server using Dynamic Host Configuration Protocol (DHCP). Even though IP addresses assigned using DHCP may stay the same for long periods of time, they can generally change. In some cases, a network administrator may implement dynamically assigned static IP addresses. In this case, a DHCP server is used, but it is specifically configured to always assign the same IP address to a particular computer. This allows static IP addresses to be configured centrally, without having to specifically configure each computer on the network in a manual procedure.

In the absence or failure of static or stateful (DHCP) address configurations, an operating system may assign an IP address to a network interface using state-less auto-configuration methods, such as Zeroconf.

Uses of dynamic addressingEdit

Dynamic IP addresses are most frequently assigned on LANs and broadband networks by Dynamic Host Configuration Protocol (DHCP) servers. They are used because it avoids the administrative burden of assigning specific static addresses to each device on a network. It also allows many devices to share limited address space on a network if only some of them will be online at a particular time. In most current desktop operating systems, dynamic IP configuration is enabled by default so that a user does not need to manually enter any settings to connect to a network with a DHCP server. DHCP is not the only technology used to assign dynamic IP addresses. Dialup and some broadband networks use dynamic address features of the Point-to-Point Protocol.

Sticky dynamic IP address Suleras:Anchor Edit

A sticky dynamic IP address is an informal term used by cable and DSL Internet access subscribers to describe a dynamically assigned IP address which seldom changes. The addresses are usually assigned with DHCP. Since the modems are usually powered on for extended periods of time, the address leases are usually set to long periods and simply renewed. If a modem is turned off and powered up again before the next expiration of the address lease, it will most likely receive the same IP address.

Address autoconfigurationEdit

RFC 3330 defines an address block,, for the special use in link-local addressing for IPv4 networks. In IPv6, every interface, whether using static or dynamic address assignments, also receives a local-link address automatically in the block fe80::/10.

These addresses are only valid on the link, such as a local network segment or point-to-point connection, that a host is connected to. These addresses are not routable and like private addresses cannot be the source or destination of packets traversing the Internet.

When the link-local IPv4 address block was reserved, no standards existed for mechanisms of address autoconfiguration. Filling the void, Microsoft created an implementation that is called Automatic Private IP Addressing (APIPA). Due to Microsoft's market power, APIPA has been deployed on millions of machines and has, thus, become a de facto standard in the industry. Many years later, the IETF defined a formal standard for this functionality, RFC 3927, entitled Dynamic Configuration of IPv4 Link-Local Addresses.

Uses of static addressingEdit

Some infrastructure situations have to use static addressing, such as when finding the Domain Name System (DNS) host that will translate domain names to IP addresses. Static addresses are also convenient, but not absolutely necessary, to locate servers inside an enterprise. An address obtained from a DNS server comes with a time to live, or caching time, after which it should be looked up to confirm that it has not changed. Even static IP addresses do change as a result of network administration (RFC 2072)

Suleras:Visible anchoresEdit

A public IP address in common parlance is synonymous with a, globally routable unicast IP address.Suleras:Citation needed

Both IPv4 and IPv6 define address ranges that are reserved for private networks and link-local addressing. The term public IP address often used exclude these types of addresses.

Modifications to IP addressingEdit

IP blocking and firewallsEdit

Firewalls perform Internet Protocol blocking to protect networks from unauthorized access. They are common on Suleras:As of's Internet. They control access to networks based on the IP address of a client computer. Whether using a blacklist or a whitelist, the IP address that is blocked is the perceived IP address of the client, meaning that if the client is using a proxy server or network address translation, blocking one IP address may block many individual computers.

IP address translationEdit

Multiple client devices can appear to share IP addresses: either because they are part of a shared hosting web server environment or because an IPv4 network address translator (NAT) or proxy server acts as an intermediary agent on behalf of its customers, in which case the real originating IP addresses might be hidden from the server receiving a request. A common practice is to have a NAT hide a large number of IP addresses in a private network. Only the "outside" interface(s) of the NAT need to have Internet-routable addresses.[11]

Most commonly, the NAT device maps TCP or UDP port numbers on the outside to individual private addresses on the inside. Just as a telephone number may have site-specific extensions, the port numbers are site-specific extensions to an IP address.

In small home networks, NAT functions usually take place in a residential gateway device, typically one marketed as a "router". In this scenario, the computers connected to the router would have 'private' IP addresses and the router would have a 'public' address to communicate with the Internet. This type of router allows several computers to share one public IP address.

Diagnostic toolsEdit

Computer operating systems provide various diagnostic tools to examine their network interface and address configuration. Windows provides the command-line interface tools ipconfig and netsh and users of Unix-like systems can use ifconfig, netstat, route, lanstat, ifstat, or iproute2 utilities to accomplish the task.

See alsoEdit





External linksEdit

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A sourced reference lifted electronicaly from the internet.


Angmayakda 19:38, Abril 18, 2012 (UTC)

Kamalian sa pagtukoy: Umiiral na ang mga tatak na <ref>, subalit walang natagpuang tatak na <references/>

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