A subnet mask defines which portion of the address is used to identify the network and which denotes the hosts. This is done with borrowed bits from the host portion of the IP address, and this enables a more efficient use of the network address. Multicast IP addresses have their first octets in the range 224 to 239.Ĭlass E-Reserved for future use and includes the range of addresses with a first octet from 240 to 255.Īs a concept, subnetting divides the network into smaller portions called subnets. The first octet range of 192 to 223 is a Class C address.Ĭlass D-Used for multicast. Any address whose first octet is in the range 128 to 191 is a Class B address.Ĭlass C-The first three octets denote the network address, and the last octet is the host portion. Notice that 0 is reserved as a part of the default address, and 127 is reserved for internal loopback testing.Ĭlass B-The first two octets denote the network address, and the last two octets are the host portion. Any IP address whose first octet is between 1 and 126 is a Class A address. ClassesĬlass A-The first octet denotes the network address, and the last three octets are the host portion. For more information on IP addresses, refer to Configure IP Addresses and Unique Subnets for New Users. Each of the octets can be represented in a decimal format, separated by decimal points. The IP address is generally represented with the dotted-decimal notation, where 32 bits are divided into four octets. The host (or node) address is used to identify a particular device attached to the network. The network address is used to identify the network and is common to all the devices attached to the network. Background InformationĪn IP address is 32 bits long and made up of two components, a network portion and a host portion. Refer to Cisco Technical Tips Conventions for more information on document conventions. If your network is live, ensure that you understand the potential impact of any command. All of the devices used in this document started with a cleared (default) configuration. The information in this document was created from the devices in a specific lab environment. This document is not restricted to specific software and hardware versions. There are no specific requirements for this document. Not responsible for any loss resulting from the use of this site.This document describes how IP addresses are used within hosts and subnets. Version 3.0 - Version Date: September 20, 2005 You can also donate a custom amount using the far right button (not less than $1 please, or PayPal gets most/all of your money!) In lieu of a larger donation, you may wish to consider purchasing a download license of The TCP/IP Guide. If you find The TCP/IP Guide useful, please consider making a small Paypal donation to help the site, using one of the buttons below. IP Subnet Identifiers, Subnet Addresses and Host Addresses Table 53: Subnetting Summary Table For Class B NetworksĪddress #N Formula (N=0, 1, # of Subnets-1) Then click "Add Filter." at the bottom, and add this string: Then just click OK. Or go to the Tools menu and select "Adblock Plus Preferences.". To do so, just open the Adblock menu and select "Disable on ". If you want to use this site for free, I'd be grateful if you could add the site to the whitelist for Adblock. It's priced very economically and you can read all of it in a convenient format without ads. If you like The TCP/IP Guide, please consider the download version. And I have a family to support, just like you. I don't want to go to a pay-only model like some sites, but when more and more people block ads, I end up working for free. But please understand that I am providing premium content for free that takes hundreds of hours of time to research and write. The TCP/IP Guide - IP Subnetting Summary Tables For Class A, Class B and Class C Networks
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