MACアドレスジェネレーター
テストや開発用のランダムなMACアドレスを生成
生成
使い方
値を入力
入力フィールドに数値やパラメータを入力します。
即座に結果を取得
入力するとすぐに結果が更新されます — 送信ボタンは不要です。
コピーまたは保存
結果をクリップボードにコピーするか、ワークフローで活用します。
このツールを使う理由
完全無料
隠れたコストもプレミアムプランもありません — すべての機能が無料です。
インストール不要
すべてブラウザで実行されます。ソフトウェアのダウンロードやインストールは不要です。
プライベート＆安全
データはデバイスの外に出ることはありません。サーバーにアップロードされることはありません。
モバイル対応
完全レスポンシブ対応 — スマートフォン、タブレット、デスクトップで利用できます。
MAC Addresses: Hardware Identification in Networks
Key Takeaways
- MAC (Media Access Control) addresses are 48-bit hardware identifiers assigned to network interface cards for Layer 2 communication.
- The first 3 bytes (OUI) identify the manufacturer, while the last 3 bytes are device-specific — except in randomly generated addresses.
- All MAC address generation is performed in your browser — no addresses are stored or transmitted.
MAC addresses are the physical identity of network devices, operating at Layer 2 of the OSI model. Every Ethernet frame and WiFi packet uses MAC addresses for local network delivery. Understanding MAC address structure is essential for network administration, security (MAC filtering), virtualization (VM network config), and troubleshooting connectivity issues at the data link layer.
The 48-bit MAC address space supports 281 trillion unique addresses — enough for every networked device on Earth.
Address Space
Key Concepts
MAC Address Structure
A MAC address has 6 octets (e.g., AA:BB:CC:DD:EE:FF). The first 3 octets form the OUI (Organizationally Unique Identifier) assigned to manufacturers. The last 3 are device-specific.
Unicast vs. Multicast Bit
The least significant bit of the first octet determines if the address is unicast (0, single device) or multicast (1, group of devices). Randomly generated addresses should set this bit to 0.
Local vs. Universal Bit
The second least significant bit of the first octet indicates whether the address is universally administered (0, manufacturer-assigned) or locally administered (1, custom/random).
MAC Address Randomization
Modern operating systems (iOS, Android, Windows) randomize MAC addresses when scanning for WiFi networks to prevent tracking. This uses the locally administered bit to distinguish from real hardware addresses.
Pro Tips
Set the locally administered bit (second-least significant bit of first octet) when generating random MAC addresses to avoid conflicting with real hardware.
Use consistent MAC addresses for VMs and containers in development to avoid DHCP lease issues when recreating environments.
MAC filtering provides minimal security — MAC addresses can be easily spoofed. Use 802.1X authentication for real network access control.
Common MAC address formats include colon-separated (AA:BB:CC:DD:EE:FF), hyphen-separated (AA-BB-CC-DD-EE-FF), and Cisco format (AABB.CCDD.EEFF).
All MAC address generation is performed entirely in your browser. No generated addresses are stored, logged, or transmitted to any server. Generated addresses are random and not associated with any real hardware.