So, for example, If we had a random MAC Address of A0:91:A2:01:02:03, the OUI would be A0:91:A2. The first 3 octets of the MAC address are the OUI. This is interesting because this is included in a MAC address. The IEEE makes this information available to the public, and it is possible to determine what organizations own which OUI. The IEEE assigns these unique identifiers to companies that need to include them in a product with networking capability. MAC addresses are also essential for other network protocols such as DHCP (Dynamic Host Configuration Protocol) and ARP (Address Resolution Protocol).Īn OUI is a unique identifier that identifies an organization.

This allows simple layer 2 devices to only need the first 6 bytes to forward it. The vital thing to note here is that the MAC addresses come first, and the destination is the first 6 bytes of the packet. At the top, you have the Ethernet layer, which contains a source and destination MAC addresses. For example, the screenshot below shows a Wireshark capture you can see an IPv4 source and destination addresses at the lower parts of the packet. We use the MAC for routing in the Ethernet layer (Layer 2) and it is used to directly address the hardware. In general and oversimplifying terms, this can be thought of as a unique address to identify a physical network interface, such as a wired Ethernet, Wi-Fi, or Bluetooth network card. For readability to humans, these will usually display in a series of hexadecimal octets separated by colons like the following: These will consist of 48 bits (6 bytes) of data. Today, we will explore how to look up IEEE OUI information, demonstrate examples of using this information, and some pitfalls to watch out for.Ī MAC address is a Media Access Control address. The OUI can help get a picture of the devices on the network by using the publicly available IEEE registration information related to it. Today, we will look at MAC addresses, specifically the first 3 bytes, which serve as the Organizationally Unique Identifier, or OUI for short. When it comes to reconnaissance, every little bit of information can be helpful.

Wireshark oui lookup