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Home > Success Center > IP Address Manager (IPAM) > IPAM Administrator Guide > Introduction to IPAM > Networking concepts and terminology

Networking concepts and terminology

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Created by Nanette.Neal, last modified by Nanette.Neal on Jul 13, 2016

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The following sections define the networking concepts and terminology that are used within IPAM. Some IPAM terms correspond specifically to status icons. For more information about the icons used in IPAM, see IPAM Status Icons.

Available

All addresses in defined groups, subnets, and supernets are, by default, considered Available until they are otherwise assigned unless they are typically reserved, as in the case of the network and broadcast addresses. In IPAM, available IP addresses are indicated with a gray IP icon. For more information, see IPAM Status Icons.

Classless Inter-Domain Routing (CIDR)

CIDR is the standard, scalable method for both designating and organizing IP addresses using variable length subnet masking to optimize packet routing efficiency over the Internet. In the CIDR standard, IP address blocks are represented using an IP address with a suffix, as in 214.100.48.00/20, where the suffix, /20, indicates the number of leading bits in the binary form of the IP address corresponding to the intended subnet.

The following examples, with the leading bits of the binary expansion underlined, show equivalent representations of the same subnet:

11010110.01100100.00111001.11010101 = 214.100.57.213/32

11010110.01100100.00111001.11010000 = 214.100.57.208/28

11010110.01100100.00111001.00000000 = 214.100.57.00/24

11010110.01100100.00110000.00000000 = 214.100.48.00/20

Using CIDR, network administrators have a great amount of flexibility in terms of defining the size of available IP address allocations. The basic formula for determining the size of a CIDR subnet is File:Success_Center/New_Articles/IPAM_AdminGuide_MT/010/040/08000003_62x21.png, where S = the number of available IP addresses and n = the CIDR suffix. The following table displays the correlation between the CIDR suffix (/n) and the number of available IP addresses, or hosts, for multiple, different CIDR suffixes.

CIDR Suffix (/n)

Available IP Addresses (S)

CIDR Suffix (/n)

Available IP Addresses (S)

/31

2

/22

1022 = S - 2

/30

2 = S - 2

/20

4094 = S - 2

/28

14 = S - 2

/18

16382 = S - 2

/26

62 = S - 2

/16

65534 = S - 2

/24

254 = S - 2

/12

1048574 = S - 2

Note: In subnets defined to contain more than 2 IP addresses, typically the smallest address identifies the subnet to the rest of the network and the largest address is designated as the broadcast address for all addresses contained within the subnet.

As a simple example case of CIDR notation with respect to subnets, both 214.100.50.20 and 214.100.61.45 are in the subnet 214.100.00.45/16 because they both share the same sixteen leading bits, represented by the decimal digits 214.100. These two IP addresses also exist in an even smaller subnet, 214.100.48.45/20, as revealed when the two addresses are expressed in binary, as follows, where the twenty leading bits, which are identical, are underlined:

11010110.01100100.00110010.00000100 = 214.100.50.04 11010110.01100100.00111101.00101101 = 214.100.61.45
11010110.01100100.00110000.00000000 = 214.100.48.45/20

Group

In Orion IPAM, groups serve as containers for the subnets, supernets, and even other groups you define to organize and manage your network. For more information about creating and using groups in Orion IPAM, see Managing Groups in IPAM.

Reserved

Typically, in subnets defined to contain more than 2 IP addresses, the smallest address the network address identifies the subnet to the rest of the network and the largest address the broadcast address is used to communicate to all addresses within the subnet. Both the network address and the broadcast address are considered to be Reserved for a defined subnet. In Orion IPAM, reserved IP addresses are indicated with a purple IP icon. For more information, see IPAM Status Icons.

Subnet

A subnet is any logical or physical subdivision of a network consisting of a collection of IP addresses for which some number of the leading address bits, commonly called an IP address routing prefix, are identical.

For example, as a simple case, both 214.100.50.20 and 214.100.61.45 are in the subnet 214.100.00.00/16, as they both share the same sixteen leading bits, represented by the decimal digits 214.100. Less obviously, these two IP addresses exist in an even smaller subnet, 214.100.48.00/20, as revealed when the two addresses are expressed in binary, as follows, where the twenty leading bits, which are identical, are underlined:

214.100.50.04 = 11010110.01100100.00110010.00000100

214.100.61.45 = 11010110.01100100.00111101.00101101

11010110.01100100.00110000.00000000 = 214.100.48.00/20

Organizing your network using well-defined subnets can greatly increase the efficiency and minimize the bandwidth load on your network. At a basic level, assigning IP addresses to devices on your network in such a way that highly interactive devices reside within smaller or closer subnets reduces the amount of network traffic that must be routed over longer network distances. For more information about creating and managing subnets in Orion IPAM, see Managing Subnets in IPAM.

Supernet

A supernet is an element of network organization consisting of contiguous CIDR blocks, or subnets. In networks with well defined subnets, supernets allow network administrators to consolidate and limit IP traffic to optimize routing efficiency across a network. As an example, given the following two subnets, 222.22.12.0/24 and 222.22.10.0/24, 222.22.0.0/20 is a supernet, as shown in the following expansions, where the underlining highlights the common address bits of the supernet.

222.22.12.0/24 = 11011110.00010110.00001100.00000000

222.22.10.0/24 = 11011110.00010110.00001010.00000000

222.22.0.0/20= 11011110.00010110.00000000.00000000

Transient

IPAM uses the term Transient to describe IP addresses that are dynamically assigned to devices. IP addresses designated as Transient may be assigned to any of the following types of devices:

  • Devices that power on and off regularly like laptops or some user workstations
  • Devices that enter and exit the network frequently, like laptops on a wireless network
  • Any devices on a DHCP enabled network

Transient scan intervals can be configured on a per subnet basis from the Edit Subnet window.

In IPAM, Transient IP addresses are indicated with a cyan colored IP icon. For more information, see IPAM Status Icons.

Used

The Used label is provided to indicate any IP address that is currently assigned and not otherwise available. For more information, see IPAM Status Icons.

Last modified
13:50, 13 Jul 2016

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