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%Start Classless Inter-Domain Routing Information GA S REGULAR Menu Lifewire Tech for Humans Newsletter! Search Close GO Internet, Networking, & Security &gt; Home Networking 35 35 people found this article helpful <h1> CIDR: Classless Inter-Domain Routing</h1> <h2> The basics on CIDR notation and IP addresses</h2> By Bradley Mitchell Bradley Mitchell Writer Massachusetts Institute of Technology University of Illinois An MIT graduate who brings years of technical experience to articles on SEO, computers, and wireless networking.
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%Start Classless Inter-Domain Routing Information GA S REGULAR Menu Lifewire Tech for Humans Newsletter! Search Close GO Internet, Networking, & Security > Home Networking 35 35 people found this article helpful

CIDR: Classless Inter-Domain Routing

The basics on CIDR notation and IP addresses

By Bradley Mitchell Bradley Mitchell Writer Massachusetts Institute of Technology University of Illinois An MIT graduate who brings years of technical experience to articles on SEO, computers, and wireless networking.
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Liam Wilson 2 minutes ago
lifewire's editorial guidelines Updated on April 12, 2020 Tweet Share Email Tweet Share Email Home N...
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lifewire's editorial guidelines Updated on April 12, 2020 Tweet Share Email Tweet Share Email Home Networking The Wireless Connection Routers & Firewalls Network Hubs ISP Broadband Ethernet Installing & Upgrading Wi-Fi & Wireless Classless Inter-Domain Routing was developed in the 1990s as a standard scheme for routing network traffic across the internet. Before CIDR technology was developed, internet routers managed network traffic based on the class of IP addresses.
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lifewire's editorial guidelines Updated on April 12, 2020 Tweet Share Email Tweet Share Email Home Networking The Wireless Connection Routers & Firewalls Network Hubs ISP Broadband Ethernet Installing & Upgrading Wi-Fi & Wireless Classless Inter-Domain Routing was developed in the 1990s as a standard scheme for routing network traffic across the internet. Before CIDR technology was developed, internet routers managed network traffic based on the class of IP addresses.
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Grace Liu 6 minutes ago
In this system, the value of an IP address determines its subnetwork for the purposes of routing. CI...
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Julia Zhang 3 minutes ago
It organizes IP addresses into subnetworks independent of the value of the addresses themselves. CID...
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In this system, the value of an IP address determines its subnetwork for the purposes of routing. CIDR is an alternative to IP subnetting.
Nathan Chen Member
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In this system, the value of an IP address determines its subnetwork for the purposes of routing. CIDR is an alternative to IP subnetting.
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It organizes IP addresses into subnetworks independent of the value of the addresses themselves. CIDR is also known as supernetting because it effectively allows several subnets to be grouped together for network routing. <h2> CIDR Notation </h2> CIDR specifies an IP address range using a combination of an IP address and its associated network mask.
Ryan Garcia Member
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It organizes IP addresses into subnetworks independent of the value of the addresses themselves. CIDR is also known as supernetting because it effectively allows several subnets to be grouped together for network routing.

CIDR Notation

CIDR specifies an IP address range using a combination of an IP address and its associated network mask.
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James Smith 7 minutes ago
xxx.xxx.xxx.xxx/n CIDR notation uses the above format, where n is the number of (leftmost) 1 bits in...
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Noah Davis 2 minutes ago
This notation represents the address range 192.168.12.0 to 192.168.13.255. Compared to class-based n...
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xxx.xxx.xxx.xxx/n CIDR notation uses the above format, where n is the number of (leftmost) 1 bits in the mask. 192.168.12.0/23 The example above applies the network mask 255.255.254.0 to the 192.168 network, starting at 192.168.12.0.
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xxx.xxx.xxx.xxx/n CIDR notation uses the above format, where n is the number of (leftmost) 1 bits in the mask. 192.168.12.0/23 The example above applies the network mask 255.255.254.0 to the 192.168 network, starting at 192.168.12.0.
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Amelia Singh 2 minutes ago
This notation represents the address range 192.168.12.0 to 192.168.13.255. Compared to class-based n...
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Ryan Garcia 6 minutes ago
Here's another way to visualize it: 192.168.12.0/23 = 192.168.12.0/24 + 192.168.13.0/24 ...
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This notation represents the address range 192.168.12.0 to 192.168.13.255. Compared to class-based networking, 192.168.12.0/23 represents an aggregation of the two Class C subnets 192.168.12.0 and 192.168.13.0, each having a subnet mask of 255.255.255.0.
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This notation represents the address range 192.168.12.0 to 192.168.13.255. Compared to class-based networking, 192.168.12.0/23 represents an aggregation of the two Class C subnets 192.168.12.0 and 192.168.13.0, each having a subnet mask of 255.255.255.0.
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Here&#39;s another way to visualize it: 192.168.12.0/23 &#61; 192.168.12.0/24 &#43; 192.168.13.0/24 Additionally, CIDR supports internet address allocation and message routing independent of the traditional class of a given IP address range. 10.4.12.0/22 The example above represents the address range 10.4.12.0 to 10.4.15.255 (network mask 255.255.252.0). This allocates the equivalent of four Class C networks within the much larger Class A space.
Sophia Chen Member
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Here's another way to visualize it: 192.168.12.0/23 = 192.168.12.0/24 + 192.168.13.0/24 Additionally, CIDR supports internet address allocation and message routing independent of the traditional class of a given IP address range. 10.4.12.0/22 The example above represents the address range 10.4.12.0 to 10.4.15.255 (network mask 255.255.252.0). This allocates the equivalent of four Class C networks within the much larger Class A space.
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Amelia Singh 18 minutes ago
You'll sometimes see CIDR notation used even for non-CIDR networks. In non-CIDR IP subnetting, h...
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Alexander Wang 11 minutes ago
Here are some examples: 10.0.0.0/8172.16.0.0/16192.168.3.0/24

How CIDR Works

When first...
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You&#39;ll sometimes see CIDR notation used even for non-CIDR networks. In non-CIDR IP subnetting, however, the value of n is restricted to either 8 (Class A), 16 (Class B), or 24 (Class C).
Andrew Wilson Member
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You'll sometimes see CIDR notation used even for non-CIDR networks. In non-CIDR IP subnetting, however, the value of n is restricted to either 8 (Class A), 16 (Class B), or 24 (Class C).
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William Brown 9 minutes ago
Here are some examples: 10.0.0.0/8172.16.0.0/16192.168.3.0/24

How CIDR Works

When first...
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Here are some examples: 10.0.0.0/8172.16.0.0/16192.168.3.0/24 <h2> How CIDR Works </h2> When first implemented on the internet, the core routing protocols like Border Gateway Protocol and Open Shortest Path First were updated to support CIDR. Obsolete or less popular routing protocols might not support CIDR.
Ava White Moderator
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Here are some examples: 10.0.0.0/8172.16.0.0/16192.168.3.0/24

How CIDR Works

When first implemented on the internet, the core routing protocols like Border Gateway Protocol and Open Shortest Path First were updated to support CIDR. Obsolete or less popular routing protocols might not support CIDR.
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CIDR implementations require certain support to be embedded within the network routing protocols. CIDR aggregation requires the network segments involved to be contiguous (numerically adjacent) in the address space.
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CIDR implementations require certain support to be embedded within the network routing protocols. CIDR aggregation requires the network segments involved to be contiguous (numerically adjacent) in the address space.
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Sebastian Silva 17 minutes ago
CIDR cannot, for example, aggregate 192.168.12.0 and 192.168.15.0 into a single route unless the int...
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Isaac Schmidt 11 minutes ago
Mainstream consumer routers often don't support CIDR, therefore private networks including home netw...
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CIDR cannot, for example, aggregate 192.168.12.0 and 192.168.15.0 into a single route unless the intermediate .13 and .14 address ranges are included. All internet WAN or backbone routers — those that manage traffic between internet service providers — generally support CIDR to achieve the goal of conserving IP address space.
Christopher Lee Member
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CIDR cannot, for example, aggregate 192.168.12.0 and 192.168.15.0 into a single route unless the intermediate .13 and .14 address ranges are included. All internet WAN or backbone routers — those that manage traffic between internet service providers — generally support CIDR to achieve the goal of conserving IP address space.
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Mainstream consumer routers often don't support CIDR, therefore private networks including home netw...
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Mainstream consumer routers often don't support CIDR, therefore private networks including home networks and even small public networks (LANs) often don't employ it. <h2> CIDR and IPv6 </h2> IPv6 uses CIDR routing technology and CIDR notation in the same way as IPv4. IPv6 was designed for fully classless addressing.
Lucas Martinez Moderator
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Mainstream consumer routers often don't support CIDR, therefore private networks including home networks and even small public networks (LANs) often don't employ it.

CIDR and IPv6

IPv6 uses CIDR routing technology and CIDR notation in the same way as IPv4. IPv6 was designed for fully classless addressing.
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