What is Binary?

What is Binary?

Binary is a number system that uses only two digits: 0 and 1. Unlike our everyday decimal system which uses ten digits (0-9), binary operates on base-2 mathematics. This system is fundamental to all computer operations, including networking equipment like Cisco routers and switches.

Every piece of data in a computer system is ultimately represented as a series of binary digits, called bits. Understanding binary is crucial for network professionals because it directly relates to how IP addresses work, how subnetting is calculated, and how network devices process information.

How Binary Works

In binary, each position represents a power of 2, starting from 2⁰ on the right. Here's how the first eight positions work:

Position: 8  7  6  5  4  3  2  1
Power:   2^7 2^6 2^5 2^4 2^3 2^2 2^1 2^0
Value:   128 64 32 16  8  4  2  1

To convert a binary number to decimal, you add up the values of each position where there's a 1. For example:

Binary:  1  0  1  1  0  1  0  1
Value:   128 0  32 16  0  4  0  1
Total:   128 + 32 + 16 + 4 + 1 = 181

So the binary number 10110101 equals 181 in decimal.

Binary in Networking

Binary is essential in networking for several key areas:

IP Addresses

Every IPv4 address is actually a 32-bit binary number divided into four 8-bit sections called octets. For example, the IP address 192.168.1.1 in binary is:

192.168.1.1
11000000.10101000.00000001.00000001

Subnet Masks

Subnet masks use binary to determine which portion of an IP address represents the network and which represents the host. A subnet mask like 255.255.255.0 in binary shows clearly how the network boundary is defined:

255.255.255.0
11111111.11111111.11111111.00000000

The consecutive 1s represent the network portion, while the 0s represent the host portion.

Subnetting Calculations

Understanding binary makes subnetting much easier. When you borrow bits for subnetting, you're literally changing 0s to 1s in the subnet mask. This binary manipulation determines how many subnets you can create and how many hosts each subnet can contain.

Converting Between Binary and Decimal

Decimal to Binary

To convert from decimal to binary, repeatedly divide by 2 and track the remainders:

Convert 181 to binary:
181 ÷ 2 = 90 remainder 1
90 ÷ 2 = 45 remainder 0
45 ÷ 2 = 22 remainder 1
22 ÷ 2 = 11 remainder 0
11 ÷ 2 = 5 remainder 1
5 ÷ 2 = 2 remainder 1
2 ÷ 2 = 1 remainder 0
1 ÷ 2 = 0 remainder 1

Reading remainders from bottom to top: 10110101

Binary to Decimal

To convert from binary to decimal, multiply each bit by its positional value and add them together, as shown in the earlier example.

Practice Makes Perfect

The key to mastering binary is practice. Start by memorizing the powers of 2 up to 2⁷ (128). This knowledge will make subnet calculations much faster during CCNA studies and in real-world networking scenarios.

Try converting these decimal numbers to binary:

• 192
• 168
• 255
• 128

Then verify your answers by converting back to decimal.

Why Network Engineers Need Binary

Understanding binary gives you a deeper comprehension of how network devices actually process addresses and make forwarding decisions. When you configure access control lists (ACLs), design subnets, or troubleshoot routing issues, you're working with binary operations behind the scenes.

This foundational knowledge will serve you throughout your networking career, from CCNA certification through advanced network design and troubleshooting.