A MAC (Media Access Control) address is a unique identifier assigned to a network interface controller (NIC) for use as a network address in communications within a network segment. This use is common in most IEEE 802 networking technologies, including Ethernet, Wi-Fi, and Bluetooth.
On the other hand, OUI (Organizationally Unique Identifier) is a 24-bit number that makes up the first three octets of a MAC address. It is assigned by the Institute of Electrical and Electronics Engineers (IEEE) to manufacturers of network equipment. The OUI is used to identify the manufacturer of the network card, making it easier to track down the origin of a device connected to a network.
In this article, we will take a closer look at MAC addresses and OUI values and how they are used in modern networking.
How is a MAC Address Formed?
A MAC address is a 48-bit number that is usually represented in hexadecimal form, separated by colons or dashes. The first three octets of a MAC address make up the OUI, while the last three octets represent the device identifier.
For example, a MAC address might look something like this: 00:11:22:33:44:55. The first three octets (00:11:22) represent the OUI, while the last three octets (33:44:55) represent the device identifier.
What are the Uses of OUI values?
The primary use of OUI values is to identify the manufacturer of a network device. This information can be useful in a number of ways, including:
- Tracking down the origin of a device on a network
- Determining the manufacturer of a network device that is not labeled
- Verifying that a device is authentic and not a counterfeit product
- Identifying devices that are connected to a network for security and network management purposes.
OUI values can also be used to block specific devices from connecting to a network. For example, a network administrator may choose to block all devices with a specific OUI value if they are known to be a security threat.
How is an OUI Value Assigned?
OUI values are assigned by the IEEE to manufacturers of network equipment. The process of obtaining an OUI is straightforward and involves submitting a request to the IEEE and paying a fee.
Once an OUI has been assigned, the manufacturer can use it to create unique MAC addresses for their network devices. This allows them to ensure that their devices can be easily identified on a network and can be easily tracked if necessary.
Examples of OUI Values
Below are some examples of well-known OUI values:
- 00:00:0C: Cisco Systems, Inc.
- 00:04:0F: Enterasys Networks
- 00:05:69: D-Link Corporation
- 00:06:5B: Extreme Networks, Inc.
- 00:08:74: 3Com Corporation
- 00:50:C2: Microsoft Corporation
- 00:90:27: Hewlett-Packard
- 00:A0:C9: Intel Corporation
- 00:E0:29: Sun Microsystems
- 00:E0:4C: Apple, Inc.
As you can see, OUI values can be used to identify well-known manufacturers of network devices, such as Cisco Systems, Microsoft, Intel, and Apple.
What Happens if an OUI Value is not Recognized?
If an OUI value is not recognized, it may indicate a few different things. First, it could mean that the device is a counterfeit product or that the MAC address has been altered in some way. Second, it could mean that the device is from a smaller or less well-known manufacturer that does not have an assigned OUI value.
In either case, the device should be carefully scrutinized to determine if it poses a security risk to the network. If the device is found to be a security threat, the network administrator may choose to block it from connecting to the network.
OUI Lookup Tools
There are a number of OUI lookup tools available that can be used to find the manufacturer of a device based on its MAC address. These tools are particularly useful when trying to identify a device that is not labeled or when trying to verify the authenticity of a device.
One popular OUI lookup tool is the Wireshark OUI lookup tool. This tool allows you to enter the first three octets of a MAC address and returns the manufacturer of the device.
Another popular tool is the MAC Address Vendors List, which is a database of OUI values and the manufacturers that they correspond to. This database is constantly updated and is available for free online.
OUI values play an important role in modern networking, as they allow manufacturers to create unique MAC addresses for their network devices and allow network administrators to easily identify and track devices on a network. Whether you are a network administrator or simply someone who is curious about the origin of a device connected to your network, understanding OUI values and how to use them can be a valuable tool.