Understanding IP Addressing and CIDR Charts — RIPE Network
Every device connected to the Internet needs to have an identifier. Internet Protocol (IP) addresses are the numerical addresses used to identify a particular piece of hardware connected to the Internet.
The two most common versions of IP in use today are Internet Protocol version 4 (IPv4) and Internet Protocol version 6 (IPv6). Both IPv4 and IPv6 addresses come from finite pools of numbers.
For IPv4, this pool is 32-bits (232) in size and contains 4, 294, 967, 296 IPv4 addresses. The IPv6 address space is 128-bits (2128) in size, containing 340, 282, 366, 920, 938, 463, 463, 374, 607, 431, 768, 211, 456 IPv6 addresses.
A bit is a digit in the binary numeral system, the basic unit for storing information.
Not every IP address in the IPv4 or IPv6 pool can be assigned to the machines and devices used to access the Internet. Some IP addresses have been reserved for other uses, such as for use in private networks. This means that the total number of IP addresses available for allocation is less than the total number in the pool.
Network prefixes
IP addresses can be taken from the IPv4 or the IPv6 pool and are divided into two parts, a network section and a host section. The network section identifies the particular network and the host section identifies the particular node (for example, a certain computer) on the Local Area Network (LAN).
Allocation
IP addresses are assigned to networks in different sized ‘blocks’. The size of the ‘block’ assigned is written after an oblique (/), which shows the number of IP addresses contained in that block. For example, if an Internet Service Provider (ISP) is assigned a “/16”, they receive around 64, 000 IPv4 addresses. A “/26” network provides 64 IPv4 addresses. The lower the number after the oblique, the more addresses contained in that “block”.
IPv4
The size of the prefix, in bits, is written after the oblique. This is called “slash notation”. There is a total of 32 bits in IPv4 address space. For example, if a network has the address “192. 0. 2. 0/24”, the number “24” refers to how many bits are contained in the network. From this, the number of bits left for address space can be calculated. As all IPv4 networks have 32 bits, and each “section” of the address denoted by the decimal points contains eight bits, “192. 0/24” leaves eight bits to contain host addresses. This is enough space for 256 host addresses. These host addresses are the IP addresses that are necessary to connect your machine to the Internet.
A network numbered “10. 0/8” (which is one of those reserved for private use) is a network with eight bits of network prefix, denoted by “/8” after the oblique. The “8” denotes that there are 24 bits left over in the network to contain IPv4 host addresses: 16, 777, 216 addresses to be exact.
Classless Inter-Domain Routing (CIDR) Chart
The Classless Inter-Domain Routing (CIDR) is commonly known as the CIDR chart and is used by those running networks and managing IP addresses. It enables them to see the number of IP addresses contained within each “slash notation” and the size of each “slash notation” in bits.
Download: IPv4 CIDR Chart (PDF)
IPv6
IPv6 is similar to IPv4, but it is structured so that all LANs have 64 bits of network prefix as opposed to the variable length of network prefix1 that IPv4 networks have. All IPv6 networks have space for 18, 446, 744, 073, 709, 551, 616 IPv6 addresses.
Download: IPv6 Chart (PDF)
Currently, most ISPs assign /48 network prefixes to subscribers’ sites (the End Users’ networks). Because all IPv6 networks have /64 prefixes, a /48 network prefix allows 65, 536 LANs in an End User’s site.
The current minimum IPv6 allocation made by the RIPE NCC is a /32 network prefix. If the LIR only made /48 assignments from this /32 network prefix, they would be able to make 65, 536 /48 assignments. If they decided to only assign /56 network prefixes they would have 24 bits available to them, and so could make 16, 777, 216 /56 assignments.
For example, if a /24 IPv6 allocation is made to an LIR, it would be able to make 16, 777, 216 /48 assignments or 4, 294, 967, 296 /56 assignments.
To give some perspective, it is worth noting that there are 4, 294, 967, 296 IPv4 addresses in total, significantly less than the number of IPv6 addresses.
IPv6 Relative Network Sizes
/128
1 IPv6 address
A network interface
/64
1 IPv6 subnet
18, 446, 744, 073, 709, 551, 616 IPv6 addresses
/56
256 LAN segments
Popular prefix size for one subscriber site
/48
65, 536 LAN segments
/32
65, 536 /48 subscriber sites
Minimum IPv6 allocation
/24
16, 777, 216 subscriber sites
256 times larger than the minimum IPv6 allocation
1 RFC2526, Reserved IPv6 Subnet Anycast Addresses (Proposed Standard)
IPv4 vs. IPv6 Benefits – What is it? | ThousandEyes
What is IPv6?
IPv6 is the next generation Internet Protocol (IP) address standard intended to supplement and eventually replace IPv4, the protocol many Internet services still use today. Every computer, mobile phone, home automation component, IoT sensor and any other device connected to the Internet needs a numerical IP address to communicate between other devices. The original IP address scheme, called IPv4, is running out of addresses due to its widespread usage from the proliferation of so many connected devices.
What is IPv4?
IPv4 stands for Internet Protocol version 4. It is the underlying technology that makes it possible for us to connect our devices to the web. Whenever a device accesses the Internet, it is assigned a unique, numerical IP address such as 99. 48. 227. To send data from one computer to another through the web, a data packet must be transferred across the network containing the IP addresses of both devices.
Why Support IPv6? What are the benefits of IPv6?
IPv6 (Internet Protocol version 6) is the sixth revision to the Internet Protocol and the successor to IPv4. It functions similarly to IPv4 in that it provides the unique IP addresses necessary for Internet-enabled devices to communicate. However, it does have one significant difference: it utilizes a 128-bit IP address.
Key benefits to IPv6 include:
No more NAT (Network Address Translation)
Auto-configuration
No more private address collisions
Better multicast routing
Simpler header format
Simplified, more efficient routing
True quality of service (QoS), also called “flow labeling”
Built-in authentication and privacy support
Flexible options and extensions
Easier administration (no more DHCP)
IPv4 uses a 32-bit address for its Internet addresses. That means it can provide support for 2^32 IP addresses in total â around 4. 29 billion. That may seem like a lot, but all 4. 29 billion IP addresses have now been assigned, leading to the address shortage issues we face today.
IPv6 utilizes 128-bit Internet addresses. Therefore, it can support 2^128 Internet addresses—340, 282, 366, 920, 938, 463, 463, 374, 607, 431, 768, 211, 456 of them to be exact. The number of IPv6 addresses is 1028 times larger than the number of IPv4 addresses. So there are more than enough IPv6 addresses to allow for Internet devices to expand for a very long time.
The text form of the IPv6 address is xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx, where each x is a hexadecimal digit, representing 4 bits. Leading zeros can be omitted. The double colon (::) can be used once in the text form of an address, to designate any number of 0 bits.
With Dual-IP stacks, your computers, routers, switches, and other devices run both protocols, but IPv6 is the preferred protocol. A typical procedure for businesses is to start by enabling both TCP/IP protocol stacks on the wide area network (WAN) core routers, then perimeter routers and firewalls, followed by data-center routers and finally the desktop access routers.
ThousandEyes Support for IPv6
With IPv6 becoming more prevalent in cloud provider and consumer access networks, you may already be on the path to IPv6 deployment with your network and applications.
If you are looking to understand IPv6 in your environment there are three things you should be monitoring:
IPv6 DNS resolution
IPv6 traffic paths
IPv6 BGP prefixes and routes
ThousandEyes has support for IPv6 so that organizations can utilize IPv6 across all of their test types (web, network, voice, routing) and agent types (cloud, enterprise, endpoint).
ThousandEyes Cloud Agent support for IPv6 is provided on six continents allowing global coverage for organizations. ThousandEyes also supports the use of dual-stack IPv4 and IPv6 Enterprise Agents. Enterprise Agents can have both addresses assigned and executes tests based on a user-defined preference for only IPv4, only IPv6 or a preference for IPv6.
What you need to know about IPv6 | Enable Sysadmin – Red Hat
During the year of 1994, the Internet Engineering Task Force (IETF) initiated the development of the Internet Protocol version 6 (better known as IPv6). In December 1998, the first draft became a standard for the IETF, which eventually was ratified as the Internet Standard on July 14, 2017.
The main reason for the development of IPv6 was to overcome the problem of IPv4 address exhaustion. With this issue in mind, the IETF also optimized the protocol in the general sense.
To understand the need for IPv6 and why it is the successor of IPv4, we’ll have to cover IPv4 briefly.
IPv4
First deployed in 1983 by Advanced Research Projects Agency Networks (ARPANET), IPv4 is still the most used routed protocol, despite its successor IPv6.
Here are a few facts about IPv4:
IPv4 uses a 32-bit (232) address space, meaning that a total of 4, 294, 967, 296 unique IP addresses can be assigned to hosts.
There are a number of special blocks reserved for private networks (Class A, B, and C), roughly 18 million addresses, and 270 million are reserved for multicast addresses.
IPv4 is written in a decimal notation where each octet is separated by a dot (i. e, 1. 2. 3. 4).
Internet Protocol Security (IPSec) is optional in IPv4, and the minimum fragmented packet size is 576 bytes.
Network address translation (NAT) is used to further limit IP address exhaustion.
IPv6
With the rapid growth of internet devices—otherwise known as the Internet of Things (IoT)—around the globe, more IP addresses are required for these devices to exchange data. Think about mobile phones, smartwatches, refrigerators, washing machines, smart TVs, and other items that require an IP address. All of these devices are nowadays connected to the internet and identified by a unique IP address. In this section, we’ll focus on IPv6, its features, and why it will be the Internet Protocol standard.
Before jumping into details, there are a few key features IPv6 incorporates:
IPv6 uses 128-bit (2128) addresses, allowing 3. 4 x 1038 unique IP addresses. This is equal to 340 trillion trillion trillion IP addresses.
IPv6 is written in hexadecimal notation, separated into 8 groups of 16 bits by the colons, thus (8 x 16 = 128) bits in total. An IPv6 address representation looks like this:
2001:db8:1234::f350:2256:f3dd/64
IPv6 can be configured manually, using Stateless Address Auto Configuration (SLAAC), or DHCPv6.
IPv6 has a minimum packet size of 1280 bytes consisting of a fixed 40-byte base header and 1240 bytes of payload (user data).
IPv6 is supported by many operating systems like Linux, macOS, Solaris, (Free, Open, and Net) BSD, and Windows.
Note that IPSec was once designed for IPv6 as a mandatory requirement. Today, it can be optionally used with IPv6. See RFC 6434. IPSec provides authentication and encryption using Authentication Headers (AH) and the Encapsulating Security Payload (ESP).
IPv6 addresses
An IPv6 address is written in hexadecimal notation separated by the colon symbol (:) as shown here:
2001:0db8:1234:0000:0000:f350:2256:f3dd/64
The above addresses could also be written as:
where consecutive zeros are eliminated and replaced by a double colon sign (::). It is important to note that if an address consists of multiple all-zero fields and those zeros occur in different parts of the IP, then the leftmost zeros are the ones that are compressed.
Let’s illustrate this with an example:
IPv6 address variant
IPv6 address notation
IPv6 fully written
2001:0db8:0000:0000:34f4:0000:0000:f3dd/64
IPv6 simplified
2001:db8::34f4:0000:0000:f3dd/64
IPv6 further simplified
2001:db8::34f4:0:0:f3dd/64
However, writing the IP address as 2001:db8::34f4::f3dd/64 will make it invalid since double-colon can be applied only once in the address (leftmost all-zeros).
The IPv6 address consists mainly of two 64-bit segments where the higher part of the bits is classified as the network part, and the lower 64 bits are classified as the client ID. The network part is subdivided into the Global Unicast Address (GUA) and subnet ID. This information can be simplified by the following picture:
It is worth noting that IPv6 has no notion of subnet masks like IPv4 has. Rather, a Classless Inter-Domain Routing (CIDR) notation is used. Examples are:
2001:581:f3d1:241f::/64
2001:db8:1234::/48
2a01:1b0::/32
2000::/3
From the end-user/end-site perspective, the network part (or network ID) is provided by your Internet Service Provider (ISP) and is static. If your ISP aggregates a /48 prefix to you, then 16-bit addresses could be used to create 216 (65535) subnets, where each subnet will be able to support 26418, 446, 744, 073, 709, 551, 616 or 1. 844674407×10¹⁹ IP addresses.
Now we know the basics of IPv6, let’s see what address types exist out there.
IPv6 address types
The following address types exist in the IPv6 ecosystem:
Unicast
Multicast
Anycast
The Unicast address type is probably the most important one. It distinguishes itself by these sub-type addresses:
Global Unique Addresses: Globally reachable. Examples:
2a01:388:3d11:f124::/64
Link-local addresses: Required on every IPv6-enabled interface, but packets cannot leave or enter the interface. This address is mostly used by software applications and starts with:
fe80::/10
Site-local addresses: Deprecated, see RFC 3879.
Loopback address: This is the address we know as 127. 0. 1/8 in IPv4, and it is written as follows in IPv6:::1/128
Unique local addresses: Routable only within the scope of the organization. These addresses are not routable globally. IPv4 equivalent private ranges are 10. 0/8, 192. 168. 1. 0/24, and so on. Unique local addresses in IPv6 start with:
fc00::/7
Multicast is the technique used to send a packet from one source (or multiple sources) to multiple destinations (receivers). In its simplest form, a multicast flow is as follows. First, a host sends an ICMPv6 packet (host solicitation) to the router(s) multicast group. Then, a router responds to this request and sends a Router Advertisement (RA) packet back to the client along with configuration parameters:
The multicast address range is ff00::/8. The first 8 bits are always ff (in binary 1111 1111).
The Anycast address behaves similarly to the Multicast address, except for the following. A packet sent from a client goes to a single selected destination and not to the whole group identified by the same destination address. The receiving endpoint is selected based on the least expensive routing metric. The router uses the equal-cost multi-path to do this:
Conclusion
Eventually, we will all be using IPv6. The sooner you understand how this address space works, and how to implement IPv6 in your own networks, the better.
Frequently Asked Questions about how many ip addresses in ipv4 vs ipv6
How many more IP addresses are there in IPv6 than IPv4?
IPv6 utilizes 128-bit Internet addresses. Therefore, it can support 2^128 Internet addresses—340,282,366,920,938,463,463,374,607,431,768,211,456 of them to be exact. The number of IPv6 addresses is 1028 times larger than the number of IPv4 addresses.
How many IP addresses are there in IPv6?
IPv6 uses 128-bit (2128) addresses, allowing 3.4 x 1038 unique IP addresses. This is equal to 340 trillion trillion trillion IP addresses. IPv6 is written in hexadecimal notation, separated into 8 groups of 16 bits by the colons, thus (8 x 16 = 128) bits in total.Sep 24, 2019
How many IPv4 addresses are there?
There are only about 4.3 billion possible IPv4 addresses, which engineers assumed would be more than enough in the 1990s. With IPv6, there are about 340 trillion trillion trillion combinations — specifically: 340,282,366,920,938,463,463,374,607,431,768,211,456.Jul 2, 2015