Add articles on MAC addresses in German and English

- Created a new German article titled "MAC Adresse - Was ist das?" covering the definition, structure, and usage of MAC addresses, including commands for displaying and changing MAC addresses, as well as ARP spoofing.
- Created a new English article titled "MAC address – what is it?" with similar content, providing an overview of MAC addresses, their structure, and related commands for different operating systems.

Author: marci

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assets/images/posts/it-security/Unbenanntes-Diagramm.jpg

@@ -0,0 +1,160 @@
+---
+title: MAC Adresse - Was ist das?
+date: 2019-02-15
+categories:
+  - Netzwerk
+  - Tutorials
+tags:
+  - firewall
+  - netzwerk
+  - security
+  - tutorials
+description: Was ist eine MAC-Adresse und wofür wird diese verwendet?
+preview: ../../../assets/images/posts/it-security/mac_adressen.jpg
+hero: /images/posts/it-security/mac_adressen.jpg
+menu:
+  sidebar:
+    name: Was ist eine MAC-Adresse und wofür wird diese verwendet?
+    identifier: mac
+    parent: security
+keywords:
+  - mac adresse
+---
+
+## MAC Adressen 
+
+Was ist eine **MAC Adresse** und wofür wird diese gebraucht? Diese Fragen und weitere Begriffe und Funktion rund um das Thema MAC Adressen möchte ich gerne in diesem Artikel erklären. 
+
+## Was ist eine MAC Adresse? 
+
+Zur Identifikation eines netzwerkfähigen Geräts (Host) im Netzwerk dient die **MAC Adresse**. Diese Adresse ist in eigentlich einmalig (dazu später mehr) und stellt die eindeutige Adressierbarkeit eines Geräts sicher.  
+
+## Aufbau
+
+Diese Adresse besteht aus einer 48-Bit langen Adresse und sollte weltweit einmalig sein. Diese Adresse wird im OSI-Modell der Sicherungsschicht 2 (Data-Link-Layer) zugeordnet um eine Adressierung im Netzwerk zu gewährleisten.  
+
+Dargestellt wird die Adresse in der Regel in der hexadezimalen Schreibweise (siehe Bild “Aufbau einer MAC-Adresse") und wird in Bytes getrennt durch einen Doppelpunkt oder Bindestrich dargestellt. Diese Schreibweise / Darstellungsweise nennt man das _kanonisches Format_ und wird in der Regel auch zur Darstellung verwendet.
+
+
+![MAC-Address Aufbau](/images/posts/it-security/Unbenanntes-Diagramm.jpg)
+
+
+Aufbau einer MAC Adresse
+
+
+
+Die ersten 24 Bit sind fest den verschiedenen Herstellern (Herstellerkennung) zugeordnet und werden von der IEEE (Institute of Electrical and Electronics Engineers) vergeben. Diese Herstellerkennung wird auch Organizationally Unique Identifier (OUI) genannt und kann Online in einer Hersteller-Datenbank abgerufen werden. 
+
+Die hinteren 24 Bit wird als Organizationally Unique Address (OUA) bezeichnet und können vom Hersteller frei, aber nur einmalig für die Geräteklasse vergeben werden. 
+
+## Broadcast Adresse
+
+Als Broadcast Adresse wird eine Pseudo-Adresse bezeichnet, wo alle 48 Bits auf "1" geschaltet sind,
+
+**Broadcast Cast MAC-Adresse:**
+
+```sh
+ff-ff-ff-ff-ff-ff und in Bit-Form 11111111 11111111 11111111 11111111 11111111 11111111	
+```
+
+und im LAN an alle Geräte verschickt wird, aber nicht in andere LAN´s gesendet werden kann.
+
+### Link zur Hersteller Datenbank von der IEEE: 
+
+[https://regauth.standards.ieee.org/standards-ra-web/pub/view.html#registries](https://regauth.standards.ieee.org/standards-ra-web/pub/view.html#registries)
+
+## Eigene MAC-Adresse anzeigen 
+
+Um die Adresse von eurem Gerät anzuzeigen gibt es ja nach Betriebssystem verschiedene Befehle die ihr in der Kommandozeile (CMD, Powershell, Shell) eingeben könnt. Die Befehle zur Anzeige der Adresse lauten für die einzelnen Systeme wie folgt: 
+
+### Windows physikalische Adresse
+
+Zuerst mit der Tastenkombination Windows-Taste+R die Kommandozeile (CMD) öffnen und dann den folgenden Befehl eingeben:
+
+```msdos
+ipconfig /all
+```
+
+
+
+### Eigene Adresse unter FreeBSD anzeigen
+
+```sh
+ipconfig -a
+```
+
+### Eigene Adresse unter Linux anzeigen
+
+```sh
+ip a
+
+ip link show <Gerät>
+```
+
+Wichtig ist generell, dass man natürlich auch das richtige Netzwerkgerät ausliest, da die Rechner meistens mehrere Netzwerkadapter besitzen (z.B. WLAN).
+
+Solltet ihr die IP-Adresse trotz der oberen Befehle nicht auslesen können, dann nutzt ein Crossover-Kabel das ihr mit einem Rechner verbindet. Somit sind dann beide Geräte im gleichen Netzwerksegment und nutzt dann die folgenden Befehle:
+
+#### Windows
+
+```msdos
+arp -a
+```
+
+#### FreeBSD
+
+```sh
+arp -a
+```
+
+#### Linux
+
+```sh
+arp -a
+ip neigh
+```
+
+
+## Ändern einer MAC-Adresse 
+
+Das ändern der Adresse kann in manchen Situationen sinnvoll sein. Wenn du zum Beispiel ein Hochverfügbarkeitsszenario nutzen möchtest, dann kann das ändern der Adresse sehr sinnvoll sein. Sollte in einem Redundanz-Verbund ein Server ausfallen, so kann durch das Ändern der MAC-Adresse auf dem Ersatzserver, ein umständliches umkonfigurieren des Systems dadurch erspart bleiben. Genauso kannst du auch andere Ersatzgeräte im Netzwerk so umstellen.
+
+### Die folgenden Befehle kannst du hierfür nutzen
+
+#### Windows
+
+```msdos
+Registery-Eintrag ändern oder auch falls angeboten in der Systemsteuerung
+```
+
+#### Linux
+
+```sh
+ifconfig <Device> hw ether <MAC-Adresse neu>
+```
+
+#### FreeBSD
+
+```sh
+ifconfig <Device> link <MAC-Adresse neu>
+```
+
+## ARP-Spoofing (böswilliges ändern) 
+
+Zu guter Letzt gehe ich hier noch auf das böswillige ändern einer MAC-Adresse ein. Diese Methode wird bei Man-in-the-Middle Attacken genutzt.
+
+Hier wird auch die Adresse im ARP-Cache gesetzt und so eine manipulierte ARP-Nachricht von Host A an Host B verschickt. Diesem Host B wird somit die Adresse des Angriffs-Device untergejubelt, wobei dieser wiederum alle zukünftigen Pakete an den Angreifer-Gerät sendet und nicht vorgesehen an Host A.
+
+Solch ein kompromittierten ARP-Cache ist gut dadurch erkennbar, dass alle IP-Adressen auf eine MAC-Adresse zeigen. Ein Beispiel siehst du im nächsten Abschnitt.
+
+### Beispiel für ein ARP-Spoofing im ARP-Cache
+
+```sh
+RE1:~# arp -a
+? (192.168.1.10) auf 00:2c:33:2f:7e:88 [ether] auf eth0
+? (192.168.1.11) auf 00:2c:33:2f:7e:88 [ether] auf eth0
+? (192.168.1.12) auf 00:2c:33:2f:7e:88 [ether] auf eth0
+? (192.168.1.13) auf 00:2c:33:2f:7e:88 [ether] auf eth0
+```
+
+

assets/images/posts/it-security/mac_adressen.jpg

@@ -0,0 +1,113 @@
+---
+title: MAC address – what is it?
+date: 2019-02-15
+categories:
+  - Network
+  - Tutorials
+tags:
+  - firewall
+  - network
+  - security
+  - tutorials
+description: What is a MAC address and what is it used for?
+preview: ../../../assets/images/posts/it-security/mac_adressen.jpg
+hero: /images/posts/it-security/mac_adressen.jpg
+menu:
+  sidebar:
+    name: What is a MAC address and what is it used for?
+    identifier: mac
+    parent: security
+keywords:
+  - mac address
+lastmode: 2025-07-28T14:26:58.650Z
+---
+## MAC addresses
+What is a **MAC address** and what is it used for? In this article, I would like to explain these questions and other terms and functions related to MAC addresses.
+## What is a MAC address?
+The **MAC address** is used to identify a network-enabled device (host) in a network. This address is actually unique (more on this later) and ensures that a device can be addressed unambiguously.  
+## Structure
+This address consists of a 48-bit address and should be unique worldwide. This address is assigned to layer 2 (data link layer) in the OSI model to ensure addressing in the network.
+  
+The address is usually represented in hexadecimal notation (see image “Structure of a MAC address”) and is represented in bytes separated by a colon or hyphen. This notation/representation is called the _canonical format_ and is usually also used for representation.
+
+![MAC address structure](images/posts/it-security/Unbenanntes-Diagramm.jpg)
+
+Structure of a MAC address
+
+
+The first 24 bits are permanently assigned to the various manufacturers (manufacturer identification) and are allocated by the IEEE (Institute of Electrical and Electronics Engineers). This manufacturer identification is also called the Organizationally Unique Identifier (OUI) and can be found online in a manufacturer database. 
+The last 24 bits are referred to as the Organizationally Unique Address (OUA) and can be assigned freely by the manufacturer, but only once for each device class.
+## Broadcast address
+A broadcast address is a pseudo-address where all 48 bits are set to “1”.
+
+**Broadcast MAC address:**
+
+```sh
+ff-ff-ff-ff-ff-ff and in bit form 11111111 11111111 11111111 11111111 11111111 11111111 
+```
+and is sent to all devices in the LAN, but cannot be sent to other LANs.
+### Link to the IEEE manufacturer database:
+[https://regauth.standards.ieee.org/standards-ra-web/pub/view.html#registries](https://regauth.standards.ieee.org/standards-ra-web/pub/view.html#registries)
+## Display your own MAC address
+To display the address of your device, there are different commands depending on your operating system that you can enter in the command line (CMD, Powershell, Shell). The commands for displaying the address are as follows for the individual systems:
+### Windows physical address
+First, open the command line (CMD) with the key combination Windows key+R and then enter the following command:
+
+```msdos
+ipconfig /all
+```
+
+
+### Display your own address under FreeBSD
+```sh
+ipconfig -a
+```
+### Display your own address under Linux
+```sh
+ip a
+ip link show <device>
+```
+It is important to select the correct network device, as computers usually have multiple network adapters (e.g., Wi-Fi).
+If you are unable to read the IP address using the above commands, use a crossover cable to connect the two computers. This will place both devices in the same network segment, allowing you to use the following commands:
+#### Windows
+```msdos
+arp -a
+```
+#### FreeBSD
+```sh
+arp -a
+```
+#### Linux
+```sh
+arp -a
+ip neigh
+```
+
+## Changing a MAC address
+Changing the address can be useful in some situations. For example, if you want to use a high-availability scenario, changing the address can be very useful. If a server fails in a redundancy network, changing the MAC address on the replacement server can save you the hassle of reconfiguring the system. You can also change other replacement devices in the network in the same way.
+### You can use the following commands for this
+#### Windows
+```msdos
+Change the registry entry or, if offered, in the Control Panel
+```
+#### Linux
+```sh
+ifconfig <Device> hw ether <New MAC address>
+```
+#### FreeBSD
+```sh
+ifconfig <Device> link <New MAC address>
+```
+## ARP spoofing (malicious modification)
+Last but not least, I will discuss the malicious modification of a MAC address. This method is used in man-in-the-middle attacks.
+Here, the address is also set in the ARP cache, and a manipulated ARP message is sent from host A to host B. Host B is thus given the address of the attacking device, which in turn sends all future packets to the attacker's device instead of to host A as intended.
+A compromised ARP cache is easily recognizable by the fact that all IP addresses point to one MAC address. You can see an example in the next section.
+### Example of ARP spoofing in the ARP cache
+```sh
+RE1:~# arp -a
+? (192.168.1.10) on 00:2c:33:2f:7e:88 [ether] on eth0
+? (192.168.1.11) on 00:2c:33:2f:7e:88 [ether] on eth0
+? (192.168.1.12) on 00:2c:33:2f:7e:88 [ether] on eth0
+? (192.168.1.13) on 00:2c:33:2f:7e:88 [ether] on eth0
+```
+