NetDrill - Networking Fundamentals

OSI Model Drag & Drop

Drag each layer name to its correct position. Click a placed item to remove it. Note the addressing & PDU for each layer.

Layer Names

Addressing & PDU Reference

L7-5 → Data

L4 → Port Numbers / Segments

L3 → IP Address / Packets

L2 → MAC Address / Frames

L1 → Signals / Bits

Protocol & Layer Quiz

For each item, select the correct OSI layer or answer

Number Systems

Convert between binary, decimal & hexadecimal. Toggle bits to build values. Drill until it's automatic.

▶ Live Converter

DEC

BIN

HEX

▶ Bit Toggle (click bits)

= 0

▶ Hex ↔ Decimal ↔ Binary (0-15)

▶ Conversion Drill

Convert the given value to the other two bases (0-255 range)

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▶ Powers of 2 Chart

Essential for subnetting. Memorize these.

▶ Subnet Magic Number

For any CIDR prefix, the magic number = 256 - (value of the interesting octet).
Block sizes: 128, 64, 32, 16, 8, 4, 2, 1
These are the only valid subnet boundary increments.

256 - 128

128

256 - 192

64

256 - 224

32

256 - 240

16

256 - 248

8

256 - 252

4

256 - 254

2

256 - 255

1

Subnet Math Drills

Quick-fire drills to build subnetting speed. Answer and hit Enter.

CIDR ↔ Subnet Mask

Convert between CIDR notation and dotted-decimal subnet masks

Host Count & Block Size

Given a prefix, calculate usable hosts and block size

Wildcard Masks

Convert subnet mask to wildcard mask (bitwise inverse)

Network Address (AND Operation)

AND the IP with the mask to find the network address

▶ Bitwise AND Visualizer

See how IP AND Mask produces the network address, bit by bit

Subnet Calculator

Enter an IP address and CIDR prefix to calculate subnet details

▶ Input

IP Address

CIDR Prefix

▶ Results

Enter an IP and prefix to see results

▶ CIDR Cheat Sheet

Subnetting Practice

Given a CIDR address, calculate the subnet details by hand

▶ Problem

Find the subnet details for:

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Network Addr

Broadcast

Subnet Mask

Usable Hosts

First Usable

Last Usable

▶ Tips

Step 1: Convert the prefix to a subnet mask. Each octet gets 8 bits. /24 = 255.255.255.0

Step 2: AND the IP with the mask to find the network address.

Step 3: Invert the mask (wildcard) and OR with network address for broadcast.

Step 4: Usable hosts = 2^(32 - prefix) - 2 (for /31 and /32, special rules apply).

Step 5: First usable = network + 1, last usable = broadcast - 1.

Quick Reference

Common protocols, ports, and their OSI layers

Protocol	Port(s)	Layer	Transport	Description

IPv6 Basics

Key differences from IPv4 and core addressing concepts

IPv6 at a Glance

Feature	IPv4	IPv6
Address size	32 bits	128 bits
Format	Dotted decimal (192.168.1.1)	Colon hex (2001:0db8::1)
Address space	~4.3 billion	~3.4 × 10³⁸
Header size	Variable (20-60 bytes)	Fixed (40 bytes)
Broadcast	Yes	No (uses multicast)
Auto-config	DHCP	SLAAC + DHCPv6
IPsec	Optional	Built-in

Address Format

2001:0db8:85a3:0000:0000:8a2e:0370:7334
8 groups of 4 hex digits separated by colons

Shortening Rules:

Drop leading zeros in each group: 0db8 → db8
Replace one consecutive run of all-zero groups with :: (only once)
Full: 2001:0db8:0000:0000:0000:0000:0000:0001
Short: 2001:db8::1

Common Prefix Lengths

Prefix	Use	Notes
/128	Single host	Equivalent to IPv4 /32
/64	Standard subnet	Most common; required for SLAAC
/48	Site allocation	Typical enterprise assignment
/32	ISP allocation	Standard ISP prefix from RIR

Key Address Types

Address	Type	Description
`::1`	Loopback	Same as 127.0.0.1 in IPv4
`::`	Unspecified	Same as 0.0.0.0 in IPv4
`fe80::/10`	Link-local	Auto-assigned, non-routable (like 169.254.x.x)
`fc00::/7`	Unique local	Private addresses (like 10.x.x.x / 192.168.x.x)
`2000::/3`	Global unicast	Public routable addresses
`ff00::/8`	Multicast	Replaces IPv4 broadcast