Here is a sample octet conversion when not all of the bits are set to 1. This continues until the left-most bit, or most significant bit, which holds a value of 2 7.

The bit just to the left of that holds a value of 2 1. Here is how binary octets convert to decimal: The right most bit, or least significant bit, of an octet holds a value of 2 0. The value in each octet ranges from 0 to 255 decimal, or 00000000 - 11111111 binary. For this reason, an IP address is said to be expressed in dotted decimal format (for example, 172.16.81.100). Each octet is converted to decimal and separated by a period (dot). The 32 binary bits are broken into four octets (1 octet = 8 bits). The address is made up of 32 binary bits, which can be divisible into a network portion and host portion with the help of a subnet mask. Understand IP AddressesĪn IP address is an address used in order to uniquely identify a device on an IP network. There are examples included to help tie everything together. Learn how to assign each interface on the router an IP address with a unique subnet. If you do not plan to connect to the Internet, Cisco strongly suggests that you use reserved addresses from RFC 1918. If you have already received your legitimate address(es) from the Internet Network Information Center (InterNIC), you are ready to begin. Subnet mask - A 32-bit combination used to describe which portion of an address refers to the subnet and which part refers to the host. Subnet - A portion of a network that shares a particular subnet address. If definitions are helpful to you, use these vocabulary terms to get you started:Īddress - The unique number ID assigned to one host or interface in a network. 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. Prerequisites RequirementsĬisco recommends that you have a basic understanding of binary and decimal numbers. This document describes basic information needed to configure your router, such as how addresses are broken down and how subnetting works.

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