mac address assignment

MAC Addresses Explained with Examples

This tutorial explains the MAC (Media Access Control) address in detail. Learn what the MAC address is, how it is formed, and the types of MAC addresses (unicast, multicast, and broadcast).

In network, an address provides a unique identity to an end device. Unless an end device has a unique address, it can’t communicate with other devices in the network. A unique address enables an end device to send and receive data in the network.

In the LAN network, a unique address is the combination of two addresses; software address and hardware address.

Addressing in Networking Reference models

A networking reference model defines the standards, characteristics, definitions, and functionalities of the network. There are two popular networking models; the OSI Seven Layers model and the TCP/IP model.

In both models, the software address and hardware address are defined in the network layer and data link layer, respectively. In both models, the network layer and data link layer stand on the third and second positions, respectively. Because of this, both layers are also known as layer 3 and layer 2, respectively.

Software address

The software address is also known as the network layer address or layer 3 address. This address is manageable and configurable. Based on network requirements and layout, this address can be configured and assigned to an end device. Almost all modern LAN implementations use the IP protocol in the network layer. The IP protocol uses the term IP address to define the software address.

I have already explained IP addresses in the following tutorial.

IP Address Classes and Definition Explained

In this tutorial, I will explain the hardware addresses in detail.

Hardware address

The hardware address is also known as the data link layer address or layer 2 address or MAC (Media Access Control) address. From these terms, the term MAC address is commonly used to refer to the hardware address. Unlike the IP address or software address, this address can’t be configured or managed. When you purchase a new NIC (Network Interface Card), or any device which has onboard NICs, it comes with a pre-configured MAC address.

A MAC address is 6 bytes (48 bits) long address in the binary numbers. MAC addresses are written in the hexadecimal format. The hexadecimal format uses the base-16 to refer to numbers. If we divide the total available length (48 bits) in binary numbers by the base (base-16) that is used to write a number in hexadecimal format, we get the total digits (12 = 48 ÷ 16) of that number in the hexadecimal format. Thus, if we write a 6 bytes (48bits) long binary MAC address in hexadecimal format, we get a 12 digits long hexadecimal number.

For convenience and easier readability, when writing a MAC address in hexadecimal format, extra space or periods or colons are added after every two or four digits. For example, you can write a MAC address in the following ways.

Without any separator: - 00000ABB28FC
Extra space after every two digits: - 00 00 0A BB 28 FC
Extra space after every four digits: - 0000 0ABB 28FC
Colon after every two digits: - 00:00:0A:BB:28:FC
Colon after every four digits: - 0000:0ABB:28FC
Period after every two digits: - 00.00.0A.BB.28.FC
Period after every four digits: - 0000.0ABB.28FC

No matter which style you use to write the MAC address, or an application or networking software uses to display the MAC address, a MAC address is always processed in binary numbers only. NIC converts hexadecimal numbers of the MAC address in binary numbers before processing and using it.

Structure or format of the MAC address

As mentioned above, you can’t assign MAC address to a NIC or onboard NICs. When you purchase a new NIC or a device with onboard NICs, it arrives with a pre-configured MAC address or MAC addresses, respectively. Before we understand how manufacturers select MAC addresses for NICs, let’s briefly understand why a MAC should be unique in the LAN network.

If a LAN network has two or more NICs configured with the same MAC address then that network will not work. Let’s understand this with an example.

Suppose in a network three PCs; PC-A (11000ABB28FC), PC-B (00000ABB28FC) and PC-C (00000ABB28FC) are connected through a switch. NICs of PC-B and PC-C have the same MAC address 00000ABB28FC.

If PC-A sends a frame to the destination MAC address 00000ABB28FC , the switch fails to deliver this frame as it has two recipients of this frame.

The following image shows this example.

A LAN network does not work unless each device in the LAN network has a unique MAC address.

Now let's be back to our main question. How do manufacturers assign a unique MAC address to each NIC?

Before manufacturing NICs, every manufacturer obtains a universally unique 3-byte code, known as the organizationally unique identifier (OUI), from the IEEE. The IEEE is an international organization that regulates and maintains the namespace of MAC addresses.

After obtaining the OUI bytes, the manufacturer uses these OUI bytes at the beginning of the MAC address of all its NICs or on-board NIC devices. The manufacturer also assigns a unique hexadecimal value in the remaining bytes.

6 bytes MAC address = 3 bytes OUI number obtained from the IEEE + 3 bytes unique number assigned by the manufacturer

MAC addresses of all NICs or onboard NIC devices manufactured by the same manufacturer always start with the same 3-bytes OUI numbers. For example, suppose the IEEE assigns an OUI “0000AA” to the xyz company. Now the xyz company will use the OUI number 0000AA as the first 24 bits to build MAC addresses for its NICs or onboard NICs devices.

To keep each product separately from others, the manufacturer uses the remaining 3-bytes. Manufacturers are free to use any sequence or method on the remaining three bytes. For example, the xyz company can assign the MAC addresses to its NICs in the incremental order.

The following table extends this example and adds two more demo companies (ABC and JKL) in the example. It also shows MAC addresses of 5 NICs from each company.

Thus, this procedure ensures that no two NICs use the same MAC address in the universe.

Types of MAC address

There are three types of MAC address; unicast, multicast, and broadcast.

Unicast MAC address

Unicast MAC address represents a specific NIC or onboard NIC ports in the network. The inbuilt MAC address of a NIC is the unicast MAC address of that NIC.

Multicast MAC address

Multicast MAC address represents a group of devices (or NICs in Layer 2). The IEEE has reserved the OUI 01-00-5E (first 3-bytes or 24 bits) for the multicast MAC addresses. The remaining 24 bits are set by the network application or device that wants to send data in the group. A multicast MAC address always starts with the prefix 01-00-5E.

Broadcast MAC address

Broadcast MAC address represents all devices in the network. The IEEE has reserved the address FFFF.FFFF.FFFF as the broadcast MAC address. Any device that wants to send the data to all devices of the network, can use this address as the destination MAC address.

That’s all for this tutorial. If you like this tutorial, please don’t forget to share it with friends through your favorite social channel.

By ComputerNetworkingNotes Updated on 2024-01-02 05:30:01 IST

ComputerNetworkingNotes CCNA Study Guide MAC Addresses Explained with Examples

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To communicate or transfer data from one computer to another, we need an address. In computer networks, various types of addresses are introduced; each works at a different layer. A MAC address , which stands for Media Access Control Address, is a physical address that works at the Data Link Layer. In this article, we will discuss addressing a DLL, which is the MAC Address.

So, go through the article if you are eager to learn what is MAC address and its components.

Table of Content

What is MAC (Media Access Control) Address?

Format of mac address, types of mac address.

Reason to have both IP and MAC addresses.
Why should the MAC address be unique in the LAN network?
How do I find the MAC Address?

What is MAC Cloning?

Characteristics of mac address, advantages of mac address, disadvantages of mac address.

MAC Addresses are unique 48-bit hardware numbers of a computer that are embedded into a network card (known as a Network Interface Card ) during manufacturing. The MAC Address is also known as the Physical Address of a network device. In the IEEE 802 standard, the data link layer is divided into two sublayers:

Logical Link Control (LLC) Sublayer
Media Access Control (MAC) Sublayer

The MAC address is used by the Media Access Control (MAC) sublayer of the Data-Link Layer . MAC Address is worldwide unique since millions of network devices exist and we need to uniquely identify each.

To understand what is MAC address is, it is very important that first you understand the format of the MAC Address. So a MAC Address is a 12-digit hexadecimal number (6-bit binary number), which is mostly represented by Colon-Hexadecimal notation.

The First 6 digits (say 00:40:96) of the MAC Address identify the manufacturer, called the OUI ( Organizational Unique Identifier ). IEEE Registration Authority Committee assigns these MAC prefixes to its registered vendors.

Here are some OUI of well-known manufacturers:

The rightmost six digits represent Network Interface Controller , which is assigned by the manufacturer.

As discussed above, the MAC address is represented by Colon-Hexadecimal notation. But this is just a conversion, not mandatory. MAC address can be represented using any of the following formats:

Note: Colon-Hexadecimal notation is used by Linux OS and Period-separated Hexadecimal notation is used by Cisco Systems .

1. Unicast: A Unicast-addressed frame is only sent out to the interface leading to a specific NIC. If the LSB (least significant bit) of the first octet of an address is set to zero, the frame is meant to reach only one receiving NIC. The MAC Address of the source machine is always Unicast.

2. Multicast: The multicast address allows the source to send a frame to a group of devices. In Layer-2 (Ethernet) Multicast address, the LSB (least significant bit) of the first octet of an address is set to one. IEEE has allocated the address block 01-80-C2-xx-xx-xx (01-80-C2-00-00-00 to 01-80-C2-FF-FF-FF) for group addresses for use by standard protocols.

3. Broadcast: Similar to Network Layer, Broadcast is also possible on the underlying layer( Data Link Layer). Ethernet frames with ones in all bits of the destination address (FF-FF-FF-FF-FF-FF) are referred to as the broadcast addresses. Frames that are destined with MAC address FF-FF-FF-FF-FF-FF will reach every computer belonging to that LAN segment.

Reason to Have Both IP and MAC Addresses.

The reason for having both IP and MAC addresses lies in the way the Internet works, specifically in the structure of the OSI Model. This model is a conceptual framework that describes how data is sent and received over a network. It’s divided into seven layers, each performing specific functions.

Layer 2 uses MAC addresses and is responsible for packet delivery from hop to hop .
Layer 3 uses IP addresses and is responsible for packet delivery from end to end .

Layer 2 (Data Link Layer ) uses a MAC (Media Access Control) address . These are unique identifiers assigned to network interfaces for communications at the data link layer. The primary function of MAC addresses is to manage how data is transported from one network node to another on a direct, physical basis – this is also referred to as “hop to hop” delivery.

On the other hand, Layer 3 ( Network Layer ) uses an IP (Internet Protocol) address . These IP addresses are used to identify devices on a network and to route traffic between networks. The IP addresses ensure that the data gets from its original source reaches its final destination and it is also called “end-to-end” delivery of data.

When a computer sends data, it first wraps it in an IP header, which includes the source and destination IP addresses. This IP header, along with the data, is then encapsulated in a MAC header, which includes the source and destination MAC addresses for the current “hop” in the path.

As the data travels from one router to the next, the MAC address header is stripped off and a new one is generated for the next hop. However, the IP header, which was generated by the original computer, remains intact until it reaches the final destination. This process illustrates how the IP header manages the “end to end” delivery, while the MAC headers handle the “hop to hop” delivery.

So, Both IP and MAC addresses are essential for the functioning of the Internet. While MAC addresses facilitate the direct, physical transfer of data between network nodes, IP addresses ensure that the data reaches its final destination.

Why Should the MAC Address Be Unique in the LAN Network?

Consider a LAN ( Local Area Network ) as a large gathering where everyone is engaged in conversations. Now, let’s suppose that there are two individuals at this gathering who coincidentally share the same name. This scenario would inevitably create confusion, right? If someone calls out that name, both individuals would respond, making it challenging to discern the intended recipient of the message.

In a similar manner, within a network, each device possesses a distinct identifier referred to as a MAC (Media Access Control) address. Think of it as a unique name assigned to the device. When information is transmitted across the network, it is directed to a specific MAC address, much like a letter being addressed to a specific individual.

However, if multiple devices within the same network were to have identical MAC addresses, it would result in confusion and disrupt the network’s functioning. The network would struggle to ascertain which device should receive the transmitted information. To prevent this confusion and ensure the accurate delivery of information, it is vital for each device on a network to possess a unique MAC address.

How Do I Find the MAC Address?

A MAC address is mostly used to configure a router for a network device or during troubleshooting. The address of our computer device can be easily checked with any operating device. All the Apple devices connected to our home network contain a unique MAC address. Manufacturers may identify a MAC address by other names, such as the physical address, hardware ID, wireless ID, and Wi-Fi address.

Following are the steps which help to find MAC addresses for different OS

MAC address on Windows

Here is the Step-by-Step guide to finding MAC addresses on Windows.

Step 1 – Press Window Start or Click on Windows Key.

Step 3 – Click on cmd, the command prompt window will display,

Step 4 – In the command prompt type ipconfig/all command and then press enter.

Step 5 – As you will scroll down, each physical address is the MAC address of your device.

MAC Address on MacOS

Here is a step-by-step guide to finding MAC addresses on a Mac operating system.

Command for MAC Address in MacOS:

Step 1 – Click on System Settings.

Step 2 – In the system settings, click on the MAC network option.

Step 3 – Then go to the advanced settings.

Step 4 – Here you find your MAC address.

MAC Address on Unix/Linux

Here is a step-by-step guide to finding MAC addresses on a Unix/Linux operating system.

Command For MAC Address in Unix/Linux:

Note: LAN technologies like Token rings and Ethernet use MAC Addresses as their Physical address but there are some networks (AppleTalk) that do not use MAC addresses. for further details .

Some ISPs use MAC addresses to assign an IP address to the gateway device. When a device connects to the ISP, the DHCP server records the MAC address and then assigns an IP address. Now the system will be identified through the MAC address. When the device gets disconnected, it loses the IP address.

If the user wants to reconnect, the DHCP server checks if the device is connected before. If so, then the server tries to assign the same IP address (in case the lease period has not expired). In case the user changed the router, the user has to inform the ISP about the new MAC address because the new MAC address is unknown to ISP , so the connection cannot be established.

Or the other option is Cloning , user can simply clone the registered MAC address with ISP. Now router keeps reporting the old MAC addresses to ISP and there will be no connection issue.

The Media Access Control address (MAC address) is a unique identifier assigned to most network adapters or network interface cards (NICs) by the manufacturer for identification and use in the Media Access Control protocol sub-layer.

An Ethernet MAC address is a 48-bit binary value expressed as 12 hexadecimal digits (4 bits per hexadecimal digit). MAC addresses are in a flat structure and thus they are not routable on the Internet. Serial interfaces do not use MAC addresses. It does NOT contain a network and host portion with the address. It is used to deliver the frame to the destination device.

MAC addresses are used in LAN (Local Area Network) environments to identify devices and allow communication between them.
MAC addresses are burned into the hardware of a network interface card (NIC) and cannot be changed, except in some rare cases where the manufacturer has provided a specific tool to do so.
The first 3 bytes of a MAC address represent the manufacturer ID, while the last 3 bytes represent a unique identifier assigned by the manufacturer.
MAC addresses are often used in conjunction with ARP (Address Resolution Protocol) to resolve IP addresses to MAC addresses for communication on a LAN.
Some operating systems, such as Windows and Linux , allow you to view the MAC address of your network adapter through a command prompt or network settings.
Uniqueness: Each MAC address is unique, which means that devices on the network can be easily identified and managed.
Simplicity: MAC addresses are easy to configure and manage, and do not require any additional network infrastructure.
Compatibility: MAC addresses are widely used and supported by a variety of networking technologies and protocols, making them compatible with many different systems.
Security: MAC addresses can be used to restrict access to a network by only allowing devices with authorized MAC addresses to connect.
Fault-tolerance: In case of hardware or software failure, a device can be easily replaced without affecting the network, as long as the new device has the same MAC address as the old one.
Multicasting: MAC addresses can be used for multicasting, allowing a single packet to be sent to multiple devices at once.
Efficiency: MAC addresses allow for efficient communication on the network, as they enable devices to quickly and easily identify and communicate with each other.
Lower network overhead: MAC addresses reduce network overhead by allowing devices to communicate directly with each other without the need for additional routing or addressing.
Ease of troubleshooting: MAC addresses can be used to troubleshoot network issues by identifying the source of problems and tracking network activity.
Flexibility: MAC addresses can be used to support a variety of network configurations and topologies, including peer-to-peer, client-server, and hybrid models.
Limited address space: MAC addresses are 48-bit numbers, which means that there is a finite number of possible MAC addresses. This can lead to address conflicts if multiple devices have the same MAC address.
Spoofing: MAC addresses can be easily spoofed, allowing unauthorized devices to gain access to the network.
Inefficiency: MAC addresses are not hierarchical, which can make it difficult to efficiently manage large networks.
Static addressing: MAC addresses are typically assigned at the time of manufacture and cannot be easily changed. This can be a disadvantage in situations where devices need to be reconfigured or replaced.
Limited scope: MAC addresses are only used for identifying devices within a local network segment, and cannot be used to identify devices outside of this segment.
Hardware-dependent: MAC addresses are tied to the network interface card (NIC) of a device, which means that if the NIC fails or is replaced, the MAC address also changes.
Lack of encryption: MAC addresses are sent in plain text, which can make them vulnerable to interception and eavesdropping.
No inherent security: While MAC filtering can be used to restrict access to a network, MAC addresses themselves do not provide any inherent security features.
MAC address collisions: In rare cases, MAC addresses can collide, which can cause network disruptions and make it difficult to identify and manage devices on the network.

FAQs on MAC Address

Q1. what is mac address used for.

MAC address is used to identify devices in the same network. On the other hand, IP Addresses also did the same thing but that is used to identify Device devices globally or through its internet address.

Q2. Can we change MAC address?

No , MAC address is a permanent address of a device which is also hardcoded in the Network Interface Card (NIC). However, many drivers allow the MAC address to be changed.

Q3. What is my MAC address number?

To find the MAC address of any device, you can follow these general steps: Open the Settings app on your device. Navigate to the Network & Internet section. Select Properties. Scroll down to the bottom of the page until you find the Physical Address (MAC). For Further Details:- Check Here

Q4. Difference between MAC Address and IP Address?

The Difference points between MAC Address and IP Address MAC Address IP Address MAC Address stands for Media Access Control Address. IP Address stands for Internet Protocol Address. MAC Address is a six byte hexadecimal address. IP Address is either a four-byte (IPv4) or a sixteen-byte (IPv6) address. A device attached with MAC Address can retrieve by ARP protocol. A device attached with IP Address can retrieve by RARP protocol. NIC Card’s Manufacturer provides the MAC Address. Internet Service Provider provides IP Address. For more Details :- Check Here

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MAC Addresses With Formatting Examples

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64-Bit MAC Addresses

MAC vs. IP Addresses

MAC Address Cloning

The Media Access Control (MAC) address is a binary number used to identify computer network adapters . These numbers (sometimes called hardware addresses or physical addresses) are embedded in the network hardware during the manufacturing process or stored in firmware and designed not to be modified.

MAC addresses are also referred to as Ethernet addresses for historical reasons, but multiple types of networks use MAC addressing, including Ethernet , Wi-Fi , and Bluetooth .

The Format of a MAC Address

Traditional MAC addresses are 12-digit (6 bytes or 48 bits ) hexadecimal numbers . By convention, these addresses are usually written in one of the following three formats, although there are variations:

MM:MM:MM:SS:SS:SS
MM-MM-MM-SS-SS-SS
MMM.MMM.SSS.SSS

The leftmost six digits (24 bits), called a prefix, are associated with the adapter manufacturer (M). Each vendor registers and obtains MAC prefixes as assigned by the IEEE . Vendors often possess many prefix numbers associated with their products. For example, the prefixes 00:13:10, 00:25:9C, and 68:7F:74 (plus others) belong to Linksys (Cisco Systems).

The rightmost digits of a MAC address represent an identification number for the specific device (S). Among all devices manufactured with the same vendor prefix, each is given a unique 24-bit number. Hardware from different vendors may share the same device portion of the address.

While traditional MAC addresses are 48 bits in length, a few types of networks require 64-bit addresses instead. Zigbee wireless home automation and other similar networks based on IEEE 802.15.4, for example, require 64-bit MAC addresses to be configured on their hardware devices.

TCP/IP networks based on IPv6 also implement a different approach to communicating MAC addresses compared to mainstream IPv4. Instead of 64-bit hardware addresses, IPv6 automatically translates a 48-bit MAC address to a 64-bit address by inserting a fixed (hardcoded) 16-bit value FFFE between the vendor prefix and the device identifier. IPv6 calls these numbers identifiers to distinguish them from true 64-bit hardware addresses.

For example, a 48-bit MAC address of 00:25:96:12:34:56 appears on an IPv6 network in either of these two forms:

00:25:96:FF:FE:12:34:56
0025:96FF:FE12:3456

MAC vs. IP Address Relationship

TCP/IP networks use both MAC addresses and IP addresses but for different purposes. A MAC address remains fixed to the device's hardware, while the IP address for that same device can be changed depending on its TCP/IP network configuration. Media Access Control operates at Layer 2 of the OSI model , while Internet Protocol operates at Layer 3 . This allows MAC addressing to support other kinds of networks besides TCP/IP.

IP networks manage the conversion between IP and MAC addresses using Address Resolution Protocol (ARP). The Dynamic Host Configuration Protocol (DHCP) relies on ARP to manage the unique assignment of IP addresses to devices.

Some internet service providers link each of their residential customer accounts to the MAC addresses of the home network router or another gateway device. The address seen by the provider doesn't change until the customer replaces their gateway, such as by installing a new router. When a residential gateway is changed, the internet provider sees a different MAC address being reported and blocks that network from going online.

A cloning process solves this problem by enabling the router (gateway) to keep reporting the old MAC address to the provider even though its hardware address is different. Administrators can configure their router (assuming it supports this feature, as many do) to use the cloning option and enter the MAC address of the old gateway in the configuration screen. When cloning isn't available, the customer must contact the service provider to register their new gateway device.

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Understanding MAC Addresses: A Comprehensive Guide

Table of Contents

Introduction:

In computer networking, 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. Every device that connects to a network has a MAC address assigned to it. MAC addresses are used for numerous purposes in networking, including network address assignment, network device identification, and network security. It is an essential part of network communication, and understanding MAC addresses is crucial for troubleshooting and security purposes.

What is a MAC Address?

A MAC address is a unique identifier assigned to a network interface controller (NIC) by the manufacturer. It is used as a network address for communication within a network. MAC addresses are also known as physical addresses or hardware addresses or ethernet address.

Structure of MAC address:

A MAC address is a is a 48-bit (6-byte) address that consists of six pairs of hexadecimal numbers, separated by colons or hyphens. The first three pairs of digits identify the manufacturer of the device, while the remaining three pairs are assigned by the manufacturer to identify the specific device. Example of MAC address: 00-1B-44-11-3A-B7

How Does a MAC Address Work?

MAC addresses are used by the data link layer of the OSI model, which is responsible for transmitting data over a network. When a device wants to send data to another device on the same network, it includes the destination MAC address in the data packet. The data is then transmitted to device on the network until the device with the matching MAC address receives it.

It is important to note that MAC addresses only apply to communication within a local network segment. When data is transmitted between different network segments or over the internet, a different addressing scheme (such as IP addresses ) is used.

How are MAC Addresses Assigned?

MAC addresses are assigned by the manufacturer of the device’s network interface controller. The first three bytes or three pairs of digits in a MAC address identify the manufacturer called the OUI (Organizationally Unique Identifier), and are assigned by the Institute of Electrical and Electronics Engineers (IEEE). The remaining three bytes or pairs are assigned by the manufacturer themselves.

MAC addresses can be viewed using a variety of tools, such as the command prompt on Windows or the terminal on macOS and Linux. They can also be changed, although doing so is generally not recommended as it can cause network communication issues.

Types of MAC Addresses:

There are three types of MAC addresses: unicast, multicast, and broadcast.

Unicast address:

A unicast MAC address is used to identify a specific device on the network. When a device wants to send data to another device, it sends it to the unicast MAC address of the destination device.

Multicast address:

A multicast MAC address is used to identify a group of devices on the network. When a device wants to send data to a group of devices, it sends it to the multicast MAC address of the group. Multicast addresses are used for protocols such as ARP (Address Resolution Protocol) and DHCP (Dynamic Host Configuration Protocol).

Broadcast address:

A broadcast MAC address is used to send data to all devices on the network. When a device wants to send data to all devices on the network, it sends it to the broadcast MAC address.

MAC address and IP address:

A MAC address is a hardware address that uniquely identifies a device on a network, while an IP address is a logical address that identifies a device on a network. In other words, a MAC address identifies a device on a network, while an IP address identifies the location of a device on a network.

The relationship between a MAC address and an IP address is that a MAC address is used to identify a device on a local network, while an IP address is used to identify a device on a global network, such as the Internet. When a device sends data to another device on the local network, it uses the MAC address of the destination device. When a device sends data to another device on a global network, it uses the IP address of the destination device.

MAC Address Spoofing:

MAC address spoofing is the act of changing the MAC address of a device to impersonate another device on the network. This is often done for malicious purposes, such as to bypass security measures or to gain unauthorized access to a network. MAC address spoofing is illegal in many jurisdictions.

Conclusion:

In conclusion, MAC addresses are unique identifiers assigned to network interface controllers for use as network addresses in local network communication. They are essential for proper network communication, and can be viewed using a variety of tools. While MAC addresses are assigned by the manufacturer of the device, they can be changed, although doing so is generally not recommended. Understanding MAC addresses is crucial for troubleshooting and network security purposes.

Assigning MAC Addresses Automatically or Manually

You must have enough media access control (MAC) addresses to assign to the number of logical domains, virtual switches, and virtual networks you are going to use. You can have the Logical Domains Manager automatically assign MAC addresses to a logical domain, a virtual network ( vnet ), and a virtual switch ( vsw ), or you can manually assign MAC addresses from your own pool of assigned MAC addresses. The ldm subcommands that set MAC addresses are add-domain , add-vsw , set-vsw , add-vnet , and set-vnet . If you do not specify a MAC address in these subcommands, the Logical Domains Manager assigns one automatically.

The advantage to having the Logical Domains Manager assign the MAC addresses is that it utilizes the block of MAC addresses dedicated for use with logical domains. Also, the Logical Domains Manager detects and prevents MAC address collisions with other Logical Domains Manager instances on the same subnet. This frees you from having to manually manage your pool of MAC addresses.

MAC address assignment happens as soon as a logical domain is created or a network device is configured into a domain. In addition, the assignment is persistent until the device, or the logical domain itself, is removed.

Range of MAC Addresses Assigned to Logical Domains Software

Logical domains have been assigned the following block of 512K MAC addresses:

00:14:4F:F8:00:00 ~ 00:14:4F:FF:FF:FF

The lower 256K addresses are used by the Logical Domains Manager for automatic MAC address allocation , and you cannot manually request an address in this range:

00:14:4F:F8:00:00 - 00:14:4F:FB:FF:FF

You can use the upper half of this range for manual MAC address allocation :

00:14:4F:FC:00:00 - 00:14:4F:FF:FF:FF

Automatic Assignment Algorithm

When you do not specify a MAC address in creating logical domain or a network device, the Logical Domains Manager automatically allocates and assigns a MAC address to that logical domain or network device. To obtain this MAC address, the Logical Domains Manager iteratively attempts to select an address and then checks for potential collisions.

Before selecting a potential address, the Logical Domains Manager first looks to see if it has a recently freed, automatically assigned address saved in a database for this purpose (see Freed MAC Addresses ). If so, the Logical Domains Manager selects its candidate address from the database.

If no recently freed addresses are available, the MAC address is randomly selected from the 256K range of addresses set aside for this purpose. The MAC address is selected randomly to lessen the chance of a duplicate MAC address being selected as a candidate.

The address selected is then checked against other Logical Domains Managers on other systems to prevent duplicate MAC addresses from actually being assigned. The algorithm employed is described in Duplicate MAC Address Detection . If the address is already assigned, the Logical Domains Manager iterates, choosing another address, and again checking for collisions. This continues until a MAC address is found that is not already allocated, or a time limit of 30 seconds has elapsed. If the time limit is reached, then the creation of the device fails, and an error message similar to the following is shown.

Duplicate MAC Address Detection

To prevent the same MAC address from being allocated to different devices, one Logical Domains Manager checks with other Logical Domains Managers on other systems by sending a multicast message over the control domain's default network interface, including the address that the Logical Domain Manager wants to assign to the device. The Logical Domains Manger attempting to assign the MAC address waits for one second for a response back. If a different device on another LDoms-enabled system has already been assigned that MAC address, the Logical Domains Manager on that system sends back a response containing the MAC address in question. If the requesting Logical Domains Manager receives a response, it knows the chosen MAC address has already been allocated, chooses another, and iterates.

By default, these multicast messages are sent only to other managers on the same subnet; the default time-to-live (TTL) is 1 . The TTL can be configured using the Service Management Facilities (SMF) property ldmd/hops .

Each Logical Domains Manager is responsible for:

Listening for multicast messages

Keeping track of MAC addresses assigned to its domains

Looking for duplicates

Responding so that duplicates do not occur

If the Logical Domains Manager on a system is shut down for any reason, duplicate MAC addresses could occur while the Logical Domains Manager is down.

Automatic MAC allocation occurs at the time the logical domain or network device is created and persists until the device or the logical domain is removed.

Freed MAC Addresses

When a logical domain or a device associated with an automatic MAC address is removed, that MAC address is saved in a database of recently freed MAC addresses for possible later use on that system. These MAC addresses are saved to prevent the exhaustion of Internet Protocol (IP) addresses from a Dynamic Host Configuration Protocol (DHCP) server. When DHCP servers allocate IP addresses, they do so for a period of time (the lease time). The lease duration is often configured to be quite long, generally hours or days. If network devices are created and removed at a high rate without the Logical Domains Manager reusing automatically allocated MAC addresses, the number of MAC addresses allocated could soon overwhelm a typically configured DHCP server.

When a Logical Domains Manager is requested to automatically obtain a MAC address for a logical domain or network device, it first looks to the freed MAC address database to see if there is a previously assigned MAC address it can reuse. If there is a MAC address available from this database, the duplicate MAC address detection algorithm is run. If the MAC address had not been assigned to someone else since it was previously freed, it will be reused and removed from the database. If a collision is detected, the address is simply removed from the database. The Logical Domains Manager then either tries the next address in the database or if none is available, randomly picks a new MAC address.

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Mac Address Information Lookup

Several formats accepted: 00-1C-23-59-5A-92 , 001c23595a92 , 00:1C:23:59:5A:92
Partial searches are accepted: 001c , 2359:92
Uses several databases including NMAP, IEEE Official List, Wireshark Info , and more.
Never know what else may show up ;)

MAC address

Notational conventions

Address details.

802.11 wireless networks
IEEE 802.5 token ring
most other IEEE 802 networks
Fiber Distributed Data Interface (FDDI)
Asynchronous Transfer Mode (ATM), switched virtual connections only, as part of an NSAP address
Fibre Channel and Serial Attached SCSI (as part of a World Wide Name )
The ITU-T G.hn standard, which provides a way to create a high-speed (up to 1 gigabit/s) local area network using existing home wiring ( power lines , phone lines and coaxial cables ). The G.hn Application Protocol Convergence (APC) layer accepts Ethernet frames that use the MAC-48 format and encapsulates them into G.hn Medium Access Control Service Data Units (MSDUs).
IPv6 (Modified EUI-64 as the least-significant 64 bits of a unicast network address or link-local address when stateless autoconfiguration is used)
ZigBee / 802.15.4 / 6LoWPAN wireless personal-area networks
Packets sent to the broadcast address , all one bits, are received by all stations on a local area network. In hexadecimal the broadcast address would be FF:FF:FF:FF:FF:FF . A broadcast frame is flooded and is forwarded to and accepted by all other nodes.
Packets sent to a multicast address are received by all stations on a LAN that have been configured to receive packets sent to that address.
Functional addresses identify one or more Token Ring NICs that provide a particular service, defined in IEEE 802.5 .

Individual address block

Mac address usage in hosts, mac address usage in switches, bit-reversed notation.

Organizationally Unique Identifier
Internet Protocol version 6
Hot Standby Router Protocol or standard alternative VRRP Virtual Router Redundancy Protocol , which allows multiple routers to share one IP address and MAC address to provide router redundancy. The OpenBSD project has an open source alternative, the Common Address Redundancy Protocol ( CARP ). On Linux , iptables has a CLUSTERIP target.
NSAP address , another endpoint addressing scheme.
Sleep Proxy Service , which may 'take over' another device's MAC address during certain periods
IEEE Std 802-2001 . The Institute of Electrical and Electronics Engineers, Inc. (IEEE). 2002-02-07. p. 19. "The universal administration of LAN MAC addresses began with the Xerox Corporation administering Block Identifiers (Block IDs) for Ethernet addresses."
"Guidelines for use of the 24-bit Organizationally Unique Identifiers (OUI)" . IEEE-SA.
"Standard Group MAC Addresses: A Tutorial Guide" . IEEE-SA.
"Guidelines for Fibre Channel Use of the Organizationally Unique Identifier (OUI)" . IEEE-SA.
https://en.m.wikipedia.org/wiki/MAC_Table
"Network Interface Controller" . Wikipedia.
"Guidelines for 64-bit Global Identifier (EUI-64)" . IEEE-SA.
RFC 5342 "IANA Considerations and IETF Protocol Usage for IEEE 802 Parameters". IETF. September 2008.
IEEE-RA. "What is an Individual Address Block?" .
Configure MAB on Cisco

External links

http://standards.ieee.org/regauth/oui/oui.txt
http://www.cavebear.com/archive/cavebear/Ethernet/vendor.html
http://anonsvn.wireshark.org/wireshark/trunk/manuf
IEEE Registration Authority Tutorials
IEEE Public OUI and Company_id Assignment lookup
IEEE Public IAB list
IEEE Public OUI list
IANA Considerations and IETF Protocol Usage for IEEE 802 Parameters
IANA list of Ethernet Numbers
Wireshark 's OUI Lookup Tool and MAC address list

Information is freedom. Freedom is non-negotiable. Feel free to modify, copy, republish, sell, or use anything on this site at any time

Online Tools

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Htaccess Files from Github

Hacking and Hackers

The use of "hacker" to mean "security breaker" is a confusion on the part of the mass media. We hackers refuse to recognize that meaning, and continue using the word to mean someone who loves to program, someone who enjoys playful cleverness, or the combination of the two. -- Richard M. Stallman

How-To Geek

What exactly is a mac address used for.

Every piece of hardware on your local network has a MAC address in addition to the IP address assigned to it by the local router or server.

Quick Links

The question.

Every piece of hardware on your local network has a MAC address in addition to the IP address assigned to it by the local router or server. What exactly is that MAC address for?

Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites.

SuperUser reader Vishnu Vivek is curious about MAC addresses and their function:

I understand that IP addresses are hierarchical, so that routers throughout the internet know which direction to forward a packet. With MAC addresses, there is no hierarchy, and thus packet forwarding would not be possible. So, MAC addresses are not used for packet transfer. I don't think it sits there for no reason. So my question is, where exactly does a MAC address come into play during a packet transfer?

Where indeed? What is the specific function of the MAC address?

SuperUser contributor Werner Henze offers some insight into the function of the MAC address:

What are MAC addresses used for? MAC addresses are the low level basics that make your ethernet based network work. Network cards each have a unique MAC address. Packets that are sent on the ethernet are always coming from a MAC address and sent to a MAC address. If a network adapter is receiving a packet, it is comparing the packet's destination MAC address to the adapter's own MAC address. If the addresses match, the packet is processed, otherwise it is discarded. There are special MAC addresses, one for example is ff:ff:ff:ff:ff:ff, which is the broadcast address and addresses every network adapter in the network. How do IP addresses and MAC addresses work together? IP is a protocol that is used on a layer above ethernet. Another protocol for example would be IPX. When your computer wants to send a packet to some IP address x.x.x.x, then the first check is if the destination address is in the same IP network as the computer itself. If x.x.x.x is in the same network, then the destination IP can be reached directly, otherwise the packet needs to be sent to the configured router. Up to now things seem to have gotten worse, because now we have two IP addresses: one is the original IP packet's target address, the other is the IP of the device to which we should send the packet (the next hop, either the final destination or the router). Since ethernet uses MAC addresses, the sender needs to get the MAC address of the next hop. There is a special protocol ARP (address resolution protocol) that is used for that. Once the sender has retrieved the MAC address of the next hop, he writes that target MAC address into the packet and sends the packet. How does ARP work? ARP itself is a protocol above ethernet, like IP or IPX. When a device wants to know the MAC address for a given IP address, it sends a packet to the broadcast MAC address asking "Who has IP address y.y.y.y?" All devices receive that packet, but only the one with the IP address y.y.y.y will respond with a packet "It's me." The asking device receives the answer and now knows that the source MAC address is the right MAC address to use. Of course the result will be cached, so the device does not need to resolve the MAC address every time. Routing I almost forgot to mention: there is no routing based on MAC addresses. Low level ethernet and MAC addresses can only reach every device on the same network (cabled or wireless). If you have two networks with a router in between you cannot have a device in network A send a packet to the MAC address of a device in network B. No device in network A has the MAC address of the device in network B, so a packet to this MAC address will be discarded by all devices in the network A (also by the router). Routing is done on IP level. Simply seen the router is just doing what I described above in the section "How do IP addresses and MAC addresses work together?". The router will receive packets for its own MAC address but for a different IP address. He will then check if he can directly reach the target IP address. If so, he sends the packet to the target. Otherwise the router itself also has an upstream router configured and will send the packet to that router. Of course you can have multiple routers configured. Your home router will only have one upstream router configured, but in the internet backbone the big routers have big routing tables so they know the best ways for all packets. Other use cases for MAC addresses Network switches store a list of MAC addresses seen at every port and only forward packets to the ports that need to see the packet. Wireless access points often use MAC addresses for access control. They only allow access for known devices (MAC address is unique and identifies devices) with the correct passphrase. DHCP servers use the MAC address to identify devices and give some devices fixed IP addresses.

Have something to add to the explanation? Sound off in the the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here .

MAC Address Lookup

Find the vendor name of a device by entering an OUI or a MAC address

What does it do?

MACLookup provides an easy way to search for MAC address prefixes and matches them to the chipset's manufacturer. It uses the IEEE database.

We update MAC address lookup database as soon as we have new information from the IEEE database and Wireshark manufacturer database. There are more than 51K MAC address prefixes in the database. The database was last updated on 18 April 2024

For each search, you will always have the most accurate manufacturer, vendor or organization data, without having to worry about updating a database. You can freely download the database here

The public Rest API is available for free and provides a powerful tool for retrieving detailed vendor information about any MAC address or OUI. With this API, you can seamlessly integrate MAC address and OUI lookup functionality into your applications, services, or systems. More info...

MA-L : 35385 (68.8%)
MA-M : 5280 (10.2%)
MA-S : 5957 (11.5%)
CID : 183 (0.3%)
IAB : 4578 (9.2%)

Latest OUIs registered

Latest ouis modified.

IEEE Xplore Digital Library
IEEE Standards
IEEE Spectrum
IEEE Registration Authority

IEEE offers Registration Authority programs or registries which maintain lists of unique identifiers under standards and issue unique identifiers to those wishing to register them. The IEEE Registration Authority assigns unambiguous names to objects in a way which makes the assignment available to interested parties.

The 48-bit Extended Unique Identifier (EUI-48) and 64-bit Extended Unique Identifier (EUI-64) are globally unique identifiers used for identification of objects. Objects may be a hardware device (e.g., a network interface), a function (e.g., to identify a clock function) and similar applications. EUI-48 and EUI-64 are most commonly used for IEEE 802 universally unique MAC addresses.

EUI-48 and EUI-64 identifiers are assigned in various block sizes (MA-L, MA-M, and MA-S).

For more information, please see the tutorials on use of EUI-48 and EUI-64.

Blocks of universally unique MAC addresses/Ethernet addresses are assigned by the IEEE Registration Authority (RA). The RA makes these assignments to customers in three (3) block sizes: (MA-L = ~16 Million addresses, MA-M = ~1 Million addresses, MA-S = 4,096 addresses). Individual (i.e. single) addresses are not available from the IEEE. A 48-bit universally unique MAC address is formally referred to as an EUI-48.A 64-bit universally unique MAC address is formally referred to as an EUI-64.There is a monetary charge made by the IEEE RA for an address block.

Once you have checked against the appropriate public listing to verify your company does not already have an assignment, you may log in or create an account to request one. If the company already has an assignment, send an e-mail to the IEEE Registration Authority requesting the contact information for the existing assignment, and then make arrangements within your company to use your existing assignment.

Once the application is completed successfully, the applicant will receive an e-mail with a tracking number and payment information. The application will be processed within 7 (US) business days after receipt of payment as long as there are no problems with the information on the application or the payment. The applicant will receive an e-mail with the assignment information once the application is processed.

Consider if an existing registry is applicable. For many needs, the OUI/CID, EUI-48 or EUI-64 may meet your requirements. If different numbers are required, the IEEE Registration Authority should be consulted before balloting.

The prices for the various assignments available from the IEEE Registration Authority may be found on the IEEE RA web site for each registry.

Select assignments may be kept confidential for an annual fee.

IEEE accepts checks (payable to IEEE Registration Authority), wire transfers, as well as major credit cards and purchase orders with approved credit applications.

The difference between a public and private assignment is the format of the listing in our public listings. A public assignment lists the assignment with the company name and address. A private assignment lists the assignment with “PRIVATE” next to the number. Applicants of privately registered assignments are sent a renewal invoice annually.

The Registration Authority requires that you use 95% of an existing MA-L or MA-M assignment before an additional number can be issued to you. You must still fully exhaust your assignment before you may use the new assignment issued to you. Assignments should not be used on a per product basis or by manufacturing location. Parent and subsidiary companies can and are heavily encouraged to share assignments. Please include a Usage Percentage in section 3 of the application. Exceptions are rarely granted.

Please log in and update your company information. If there is a company name change due to purchase or sale please also email a press release or some details of the company name change to [email protected] . The company name change will not be uploaded to the public listing unless the press release or details are received.

Please see the public listings available on our web site to view public directories for each active registry.

The IEEE Registration Authority requests that any organization that intends to utilize the Organizationally Unique Identifier in the standardization of a technical area that has not previously been reviewed and approved by the IEEE RAC, please contact the IEEE Registration Authority .

IEEE standards that include OUIs and other unique numbers are subject to review by the IEEE Registration Authority Committee during ballot (Mandatory Coordination).Previously reviewed and approved standards might include new applications of OUIs and identifiers derived from OUIs. Such new applications should also be reviewed by the IEEE RAC. When revised, standards should be reviewed for consistent use of current terminology.

No. A parent company and a subsidiary company should share an assignment and if a company is sold, the assignment may be transferred to the new company. However, the assignment cannot be sold or distributed by anyone other than IEEE.

An assignment of extended unique identifiers can be used with Bluetooth. Please refer to the Bluetooth website for more information.

For further information, contact the IEEE Registration Authority .

There are currently 3 different size blocks of MAC Addresses available. They are MA-L (MAC Address Block Large), MA-M (MAC Address Block Medium) and MA-S (MAC Address Block Small).

The Registration Authority encourages organizations/companies to apply for the smallest block that will meet their needs. Example: If your organization plans to only create or distribute 500,000 devices, a MA-M assignment would suit your needs more appropriately than a MA-S assignment.

A CID, like the OUI, is a unique 24-bit identifier. A CID though, cannot be used to generate universally unique MAC addresses. Therefore, the CID is especially applicable in applications where unique MAC addresses are not required. A CID should be applicable in most other cases where an OUI is specified. The CID has been created to reduce the consumption of OUI values. A CID assignment may not be used for Bluetooth or other similar applications.

For more information, please see the tutorial “Guidelines for Use of Organizationally Unique Identifiers (OUI) and Company ID (CID).”

The Standard Group MAC Address assignment is for Standards Developers , or a Standards Development group, working to develop a new Standard. This assignment is not for companies that require MAC addresses for their products.

An OUI is a 24-bit globally unique assigned number referenced by various standards. (An OUI is assigned with a MA-L identifier block.) It can be used to identify an organization/company where a globally unique identifier is needed. The OUI is usually concatenated with other bits that are assigned by that organization in order to make a globally unique EUI-48 or EUI-64. EUI-48 and EUI-64 may be used as universally unique MAC addresses as used in the family of IEEE 802™ standards. For example, the Ethernet MAC Address is an EUI-48, unique to one particular Ethernet interface. There are other uses of the OUI however, such as its use as a company identifier in the SNAP protocol.

For more information please refer to the OUI tutorial

No. While waiting to obtain the value, a placeholder of nn-nn-nn or similar may be used. If there is already an OUI value associated with the standard, it should be used. If no such value is available then an OUI value should be obtained from the Registration Authority.

Until January 1 2014, the term “company_id” and OUI were considered equivalent to some, but the term company_id has been deprecated in favor of OUI for years. Beginning on January 1, 2014, Company ID (CID) was established as a unique registry. Either an OUI or CID may be used as a globally-unique 24-bit identifier of an organization, company, entity, manufacturer, vendor, etc.

The Individual Address Block is an inactive registry activity, which has been replaced by the MA-S registry product as of January 1,2014. The owner of an already assigned IAB may continue to use the assignment until its exhaustion. The IAB was used by organizations/companies that required less than 4097 unique 48-bit numbers (EUI-48) and thus found it hard to justify buying their own OUI. The IAB uses a MA-L (and OUI) belonging to the IEEE Registration Authority, concatenated with 12 additional IEEE-provided bits (for a total of 36 bits), leaving only 12 bits for the IAB owner to assign to their (up to 4096) individual devices. Unlike an OUI, which allows the assignee to assign values in various different number spaces (for example, EUI-48, EUI-64, and the various CDI number spaces), the Individual Address Block could only be used to assign EUI-48 identifiers. All other potential uses based on the OUI from which the IABs are allocated are reserved, and remain the property of the IEEE Registration Authority. It should also be noted that, between 2007 and September 2012, the OUI value 00:50:C2 was used for IAB assignments. After September 2012, the value 40:D8:55 was used. Applications making use of EUI-48 values assigned under an IAB should have made no assumptions about the bit pattern present in the (24-bit most-significant) OUI portion of the assigned numbers.

The OUI-36 is a deprecated registry activity name, which has been replaced by the MA-S registry product name as of January 1, 2014. This registry activity includes both a 36-bit unique number used in some standards and the assignment of a block of EUI-48 and EUI-64 identifiers by the IEEE Registration Authority. The owner of an already assigned OUI-36 registry product may continue to use the assignment.

Currently, the OUI-36 only refers to a 36-bit unique number used in some standards The OUI-36 of the MA-S assignment may be appended with 12 organization-supplied bits to form an EUI-48, or with 28 organization-supplied bits to form an EUI-64 (the identifier blocks assigned with an MA-S). .Applications making use of an MA-S should make no assumptions about the bit pattern that is present in the (24-bit most-significant) OUI portion of the assigned OUI-36.

Listing all the standards using these identifiers would be very difficult, and new uses continue to emerge; but a general listing includes:

IEEE Std 802® provides general descriptions on use of EUI-48 and EUI-64 for universally unique MAC addresses, and use in protocol identifiers. The various IEEE 802.1 standards provide specifications for bridging among networks using EUI-48 identifiers as MAC addresses.
The various active IEEE 802 network types (Ethernet, Wireless Local Area Networks, Wireless Personal Area Networks, Broadband Wireless Access, and Wireless Regional Area networks)include greater detail on use of EUI-48 or EUI-64 MAC addresses for those protocols.
Many emerging network types including IEEE 1901 Broadband over Power Line use addressing according to IEEE Std 802™.
Uses of OUIs (or the historical term “company_id”) are included in many IEEE, IETF, ITU, ISO, IEC and national standards. These standards either specifically call out use of the OUI as a 24-bit company identifier, manufacturer identifier or similar term; or define such a field and point to the IEEE RA as the source for such identifiers. It is intended that either a CID or OUI can be used in these fields. Many of these standards will be revised to also include reference to CID for these uses.
Many standards define other extensions of the OUI for unique identifiers. These identifiers are referred to as context dependent identifiers. In these context dependent identifiers, the OUI/CID are concatenated with other fields defined in the standard (e.g., to identify a design model/version, to identify software entities, to identify company specific protocols, to identify company specific management attributes, etc.)

The Length/Type Field of an Ethernet/802.3 data frame provides a context for interpretation of the Information Field that follows (i.e., protocol identification). Some values of this field are used to specify a length, the remainders are EtherType™ values. EtherTypes™ are also used with other network types and may be found encapsulated within other protocols. Refer to IEEE Std 802.3, clause 3 and especially sub-clauses 3.1.1 and 3.2.6 for use of EtherTypes™ in a Length/Type Field. See also IEEE Std 802 for a more general specification of usage.

You do not need an EtherType™ assignment to do protocol development. Because the number of EtherType™ values is limited, and not all protocol developments are successful, two EtherType™ values have been reserved for protocol development. These are formally called Local Experimental EtherTypes™, though they are also known as Playpen EtherTypes™. Use of Local Experimental EtherTypes™ is specified in IEEE Std 802a (upon revision of IEEE Std 802-2001, IEEE Std 802a will be merged into the new revision).

The requested new EtherType™ must be sufficiently well defined (e.g., a protocol defined in a standard must have progressed sufficiently for ballot). The use of the EtherType™ must also be properly defined to minimize exhaustion of available EtherTypes™ by the use of subtypes. Subtyping provides a path for enhancement without the need for the assignment of a further EtherType™ in the future. Early use of Local Experimental EtherTypes™ (Playpen EtherTypes™) helps protocol developers meet the requirements for proper design.

Subtyping most often refers to the format described in IEEE Std 802a. Here, subtyping is defined for the two specific Local Experimental EtherTypes™. The same format for subtyping is encouraged for simplicity, though not required to meet the subtyping criteria for getting an EtherType™ assignment.

Vendor Specific Protocols are protocols that an organization or company has developed for broad deployment. These protocols may use the OUI Extended EtherType™ rather than applying for a unique EtherType™ value. The OUI Extended EtherType™ is described in IEEE Std 802a. Though not currently specified in IEEE Std 802a, it is expected that either an OUI or CID can be used with the specified two-octet extension to create a globally unique protocol identifier.

Visit the EtherType™ webpage for information.

IEEE Std 1451.4 is a member of the IEEE 1451 family of smart transducer standards. Distinguishing features of IEEE 1451.4 are:

A mixed-mode communication interface (MMI), which allows digital data and analog waveforms to alternately occupy a single connection, with analog bandwidth not limited by sampling. Also defined are separate data and analog connections for transducer applications not adapted to the shared connection.
A transducer electronic data sheet (TEDS) definition, adapted to very small memories through the use of templates and containing identification and calibration data.
A template description language (TDL) allowing ongoing development of templates for diverse transducer types.
A rich template collection adapting 1451.4 to large family of transducers.
A transducer block definition allowing 1451.4 to adapt to the 1451.1 Object Model.

IEEE Std 1451.4 allows self-identification of transducers via the internal TEDS, easing bookkeeping in large measurement arrays. Stored sensitivity data allows data acquisition systems to standardize automatically to the installed transducers and track the transducers. A user field may be used to identify the transducer location in human readable format. The mixed-mode interface allows the analog waveform to be utilized in pristine form, without limitations of bandwidth introduced by sampling.

See a detailed description on IEEE Std 1451.4 operation. (PDF)

The IEEE 1451 family provides a set of common interfaces between sensors or actuators, instruments and networks. With these standard interfaces, interoperability and interchangeability of sensors or actuators across different transducer networks are thus established. These standards reduce the effort needed to develop networked smart transducers. The use of IEEE 1451.4 based transducers offers the potential for simple plug and play operation, simplifying transducer installation and system upgrade. For transducer (sensor or actuator) manufacturers, the need for major redesign of their product for compatibility with a specific instrument or network is eliminated. They can deliver products for multiple instruments and networks based on one set of standard interfaces.

For control network vendors, the availability of a large pool of network-compatible sensors and actuators will likely increase the utilization of control networks, thus creating a push-pull effort.

For system integrators, the standard interfaces will provide a significant reduction in implementation effort.

For end users, IEEE Standard 1451.4-2004 has the potential to significantly reduce the total life-cycle costs of the sensor system or network, which include installation, maintenance, and upgrade.

Within a 64-bit section of the 1451.4 TEDS, called basic TEDS, the manufacturer of the transducer is defined with a 14-bit code called the manufacturer ID, along with manufacturer-assigned transducer model number, model letter, model version number and serial number. (See IEEE Std 1451.4.2004 subclause 5.1.1, Table 2) The IEEE Registration Authority issues the manufacturer ID, to guarantee that it is unique to a manufacturer, and publishes the list of existing IEEE 1451.4 manufacturer ID’s. Data acquisition systems may make use of the basic TEDS, including manufacturer ID, and model number data in determining the transducer type and the proper template to be used in unpacking TEDS data, particularly in the case of a transducer manufacturer choosing to use a non-IEEE, or manufacturer, template. Do not confuse manufacturer ID and basic TEDS with URN, as they are two separate and distinct entities.

More details on the 1451.4 manufacturer ID and Basic TEDS. (PDF) View the IEEE listing of 1451.4 manufacturer ID codes.

Apply for an IEEE 1451.4 manufacturer ID code.

The unique registration number is a 64-bit unique identifier contained in the memory devices, or nodes, in which IEEE 1451.4 TEDS data is stored. Because multiple nodes may be arrayed in a multi-drop network format, to allow memory capacity to be increased, or other functions to be added, the URN allows a number of nodes to be individually accessed by the system. (See IEEE Std 1451.4.2004 sub clause 5.4, figure 2) See more details on the use of the URN in node devices . (PDF) Do not confuse the URN with manufacturer ID and basic TEDS, as they are two separate and distinct entities.

IEEE 1451.4 transducer manufacturers using commercially available nodes obtain a URN automatically in each node they purchase. Manufacturers wishing to emulate the IEEE 1451.4 node function with an ASIC or micro-controller, for example, must purchase a URN for each node function produced, for this purpose, the IEEE Registration Authority issues blocks of 4096 URN codes. If you are producing nodes for use with IEEE 1451.4, and wish to purchase a block of URN codes from IEEE-RA fill out our application.

Each of the standards in the IEEE 1451 family defines a storage format for data pertinent to a transducer, to be stored in the transducer. This data is called the transducer electronic data sheet, or TEDS. In general, transducer identification and calibration data are contained in the TEDS. In the case of IEEE 1451.4, the memory is large enough to contain only packed numerical data, without any units, which account for substantial memory usage in the TEDS definitions of the other standards. A template therefore defines the significance of the stored data in a 1451.4 transducer. The template is resident in the system, which reads the TEDS and unpacks the data.

View additional details on IEEE TEDS and templates (PDF)

A template is a documented definition of the placement and significance of each piece of data stored within the TEDS memory. (see IEEE Std 1451.4-2004 sub clause 5.3) The template is not contained within the TEDS data, but the TEDS data identifies which template is to be referenced in interpreting the TEDS data. Templates must be accessible to the program code, which is used to write and read the TEDS data, allowing that data to be properly packed for writing and unpacked subsequent to reading. Templates are written in the template description language (TDL) and contained in template description files. The template description file is an ASCII text file, written in TDL, and having a file name extension of .tdl. (see IEEE Std 1451.4-2004 sub clause 6.1) IEEE Standard 1451.4-2004 annex A contains several examples of the template description file. Typically the template description file is read by an application program which, at the same time, reads and interprets (or generates and writes) the bits from (to) TEDS.

Templates, or more precisely template description files, may be written by those having a transducer application not adapted to an IEEE published template. It is advisable that the library of IEEE templates be exhaustively investigated prior to undertaking writing a custom template, since it contains templates adapted to most transducer types. Using a standard template will save considerable effort by the user. The IEEE template description files can be found here.

Should writing a custom template be found necessary, please read and understand Clause 7, Template Description Language, contained in IEEE Std 1451.4-2004. Templates must be written in this language and the rules of the standard followed. More details on using TDL. (PDF) As described in the standard, a company or user can create templates for use by all to whom the template description files are distributed. A template description file may be submitted to IEEE for consideration as IEEE template by the manufacturer who developed the template of significant use, under the following condition:

The submitted template must have been in use for a sufficiently long period and by a sufficient number of users to demonstrate its effectiveness and freedom from defects.

All new templates must conform to the TDL syntax rules and pass the syntax check program located in the TDL programmer’s start-up kit described below.

Submit a new template to the IEEE-RA for consideration.

The application form and the template description file must be sent to the IEEE as indicated at the end of the form, for listing as an IEEE template. Manufacturers may elect to use non-IEEE templates for their own 1451.4 compliant products. Manufacturers choosing to use unpublished, manufacturer templates are solely responsible for the distribution and effective usage of these templates. All manufacturer templates must conform to the TDL syntax and template format guide. The format guide and TDL syntax check program are located in the TDL start-up kit.

NOTICE: The attached software is currently undergoing BETA testing. The software has not been verified for any particular purpose. USE AT YOUR OWN RISK. The software is intended solely as a tool of convenience. The software does NOT guarantee that a given product is or will be compliant with IEEE SA Standards and is NOT intended to be used, explicitly or implicitly, to certify or assure such compliance, and you shall NOT represent or imply to others that IEEE SA has tested, certified or otherwise approved of any product developed through use of this software. Download (ZIP) the programmer’s start-up kit for writing templates.

A major driving force behind the development of the IEEE 1451.4 standard was the need to minimize the amount of memory required to store a TEDS; with a stated objective of only needing 256 bits, although more are allowed. This requires a method of mapping the bits in a precise fashion. This bit mapping is accomplished through templates which are text based files written in the template description language (TDL). The TDL is a formal language similar to programming languages, but with considerably less looping and conditional control. This is because the entire purpose of the language is to map bits and not to implement general processing or mathematical capabilities.

Additional details on the functionality and syntax of the TDL. (PDF)

The IEEE Registration Authority issues IEEE 1451.4 manufacturer ID numbers on a fee basis. Apply for an IEEE 1451.4 manufacturer ID.

The IEEE Registration Authority issues IEEE 1451.4 URNs on a fee basis, in blocks of 4,096 numbers. Apply for IEEE 1451.4 URN blocks . Note: There is a maximum of 10 assignments that can be issued at one time.

The IEEE Registration Authority oversees the issuance of IEEE 1451.4 manufacturer ID numbers and URN blocks and keeps a current listing of the IEEE 1451.4 template files. To cover administrative costs, fees are charged for manufacturer ID numbers and URN blocks and to publish new templates. Payment terms are listed with the fees for each of these services.

Determine the fee or to obtain a manufacturer ID number .

Determine the fee or to obtain a URN block .

Determine the fee or to publish a new template .

The listings of existing IEEE 1451.4 manufacturer ID numbers and URN blocks are available for no charge, from the IEEE Registration Authority.

View existing manufacturer ID numbers .

There are no URN blocks assigned by the IEEE Registration Authority at this time.

The IEEE Registration Authority distributes URNs in blocks of 4,096, which is considered to be the smallest practical volume for administration purposes, at a reasonable fee for small volume users. IEEE-RA does not sanction the re-sale of partial URN blocks, due to the danger of loss of uniqueness. Several divisions within a company may share a block of URNs, however.

Manufacturers may obtain an additional manufacturer ID number only when the original has become exhausted. A statement must be furnished to the IEEE Registration Authority, verifying that 95% of the capacity of the original number has been used. The manufacturer ID occupies 14 bits of a 64-bit transducer identifier called the basic TEDS. The pool of individual transducer model numbers available to each holder of a single manufacturer ID, using the remaining 50 bits of the Basic TEDS as defined in IEEE Standard 1451.4-2004, is therefore in excess of 54.5 million model numbers. Each model may be produced up to a total in excess of 16.7 million serialized copies. By changing the version number or version letter, as defined in the Standard, a larger total of serialized copies of a given model may be supported. The total number of individual units identifiable using the IEEE Standard 1451.4-2004 basic TEDS, under a single manufacturer ID, is slightly in excess of 9 x 1014.

PSID stands for Provider Service Identifier. It is a globally unique integer value that is associated with a service being provided using a communications system such as 5.9 GHz DSRC WAVE.

The allocation of PSIDs is maintained and administered by the IEEE Registration Authority (IEEE-RA).

The Provider Service Identifier (PSID) has three uses specified in WAVE standards (see the tutorial for more detailed information). In general terms, the PSID is used to identify advertised provider services that are available; to route messages to the appropriate higher layer processes that can correctly process those messages; and to identify the permissions of participants in a service exchange.

If you or your organization are planning to develop an ITS service, then you might need a PSID.

If your service will utilize the WAVE Short Message protocol, then that service will need to be associated with a PSID. If your service utilizes IPv6 as the networking protocol, then you do not necessarily need a PSID to be allocated.

If your service will be advertised via the WAVE Service Advertisement mechanism, then your service will need a PSID.

If your service will utilize 1609.2 certificates then you will need a PSID allocated to your service.

Many PSIDs have already been allocated. If your service is based on an existing specification that uses an already allocated PSID, then you may be able to utilize that PSID.

You do not need to request both. PSIDs and ITS-AIDs share a number space, however are administered by multiple entities (e.g., IEEE Registration Authority). Applicants are encouraged to apply to a single registration entity for their service or application.

The PSID registry is maintained and administered by the IEEE Registration Authority. You may view the list of allocated PSIDs by visiting the IEEE-RA website .

Testing PSIDs have been pre-allocated for use in research and development projects. These can be used by any organization in development of their application.

You do not need to request to use a PSID allocated to testing, just start using it. For the list of allocated testing PSIDs, see public listing on the IEEE-RA website .

In the WAVE standards, a PSID is encoded into an octet string which can be from one to four octets in length. The number of octets requested depends on a number of factors which should be considered by the requester.

One and two octet PSIDs have limited availability and will be allocated on a limited basis. If your application is safety critical, and is expected to generate a large number of over-the-air messages, then your application may qualify for one of these PSIDs.

Four octet PSIDs will be suitable for most applications. If you request a PSID with fewer than four octets, then you must justify the need. The final determination regarding the PSID size that is allocated will be made by the IEEE-RA.

When PSIDs are formatted into over-the-air messages in a WAVE system, they are converted to a compact encoding known as p-encoding. See IEEE Std 1609.12 for details, and for a way to convert between the integer form and the p-encoded form.

In most cases you must complete a separate PSID request form for each PSID you are requesting.

No. If your allocation request is approved, the IEEE-RA will inform you of the value or values allocated.

If you have determined that you need to request a PSID allocation, take the following steps:

Complete and submit the PSID Request Form found on the IEEE-RA website .
You will be notified by IEEE-RA of the result of your request. This may take 90 days or more. This is a new process, and the IEEE-RA strives to respond in a timely manner.
You can appeal the decision if you don’t agree with it.
If you have questions regarding the process, see the IEEE-RA website for additional details and contact information.

The “Service/Application Name” entered on the application form should have the following characteristics:

The name should be concise.
The name should not be identical or easily confused with an existing name in the public listing of PSIDs.
The name should convey the nature of the service being provided by the application.
Include the name of, or reference to a project, e.g., in the case of limited or temporary deployments.
If the service/application is private, the name should include the name of the service provider, e.g., “( company name ) Private Service 1″.

Examples of good names include “Electronic Fee Collection”, “Traveler information and roadside signage”, “CV Pilot Traffic Signal Priority”, “Peer-to-peer distribution of Security Management Information”, and “Vehicle initiated distress notification”.

The assignee of the PSID is expected to specify what the use of the PSID means to the level of specificity necessary to enable interoperability between implementations of the service or application identified by that PSID:

If the PSID is used in a WAVE Service Advertisement (WSA), to specify what protocol is run when a response to the WSA is triggered on a User device;
If the PSID is used in a WAVE Short Message (WSM), to specify what processing is applied to the WSM payload;
If the PSID is used in an IEEE 1609.2 certificate, to specify what activities are permitted on the part of the certificate holder.

The specification may be public or private. The assignee has the authority to specify the Provider Service Context (PSC) and the Service Specific Permissions (SSP) associated with the PSID.

If your application is using 1609.2 certificates it will be necessary to identify a certificate authority that will issue certificates with your PSID. Certification of an implementation developed to a specification may be required in order to receive certificates.

For detailed information and specifications related to WAVE systems, please see IEEE Std 1609.0, IEEE Std 1609.2, IEEE Std 1609.3, IEEE Std 1609.4, IEEE Std 1609.12, and IEEE Std 802.11. See also the WAVE and PSID Tutorial .

An OpID is a 24-bit number that, per IEEE Std 802.16, is broadcast by each base station as part of its Base Station ID. An 802.16 network consists of one or more base stations operating as a coordinated system, with each base station in the coordinated network broadcasting the same OpID. The IEEE Registration Authority assigns the IEEE 802.16 Operator ID to be used as the Operator ID. See the Operator ID tutorial . (PDF)

No. Typical commercial systems providing public service require a globally unique OpID. This can be obtained from the IEEE Registration Authority. Alternately, a globally unique OpID can be derived from an operator’s E.212 MCC-MNC assignment. For networks providing service to a limited group of users where a globally unique OpID is not required by the operator, the OpID may be selected from the Public OpID pool. In this deployment scenario, the OpID may be selected from the pool to avoid having different networks in the same geographical area using the same OpID or so that a single operator can operate base stations with a single public OpID.

See the Operator ID tutorial . (PDF)

No. These are separate identifiers. They must be obtained separately and are not interchangeable.

The Base Station ID is a 48-bit number defined by IEEE Std 802.16 to be broadcast by each base station. The OpID defines the most significant 24-bits of the Base Station ID. An 802.16 network consists of one or more base stations operating as a coordinated system, with each base station in the coordinated network broadcasting the same OpID. By programming unique values in the least significant 24-bits of the Base Station ID for each base station, the Base Station ID then uniquely identifies each and every base station in the coordinated 802.16 network.

The latest available version of the OpID assignments can be found on the IEEE Registration Authority website.

No. If a company is sold, the OpID may be transferred to the new company. However, the OpID cannot be sold by anyone other than IEEE Registration Authority. See above.

Check the public listing to determine whether your company already has an assignment. If not, then complete the OpID application .

Once the application is completed successfully, the Applicant will receive an e-mail with a tracking number and payment information. The application will be processed within seven days after receipt of payment as long as there are no problems with the information on the application or the payment. The Applicant will receive an e-mail with the assignment information once the application is processed.

Yes. The IEEE Registration Authority will accept an application for an allocation of up to 100 OpIDs. If additional OpIDs are needed, you may complete an additional application. However, users of 802.16 OpIDs are encouraged to make most efficient use of this limited numbering resource. In typical deployment scenarios, the network operator will need only a single OpID, keeping in mind that a single OpID will support over 16 million Base Station IDs.

The MCC + MNC combination is a valid, globally unique 802.16 OpID. Specific coding of the MCC + MNC is required in order to be used in an 802.16 network. Coding instructions are included in the Operator ID tutorial. (PDF)

No. The formula for conversion of an E.212 MCC-MNC pair to an 802.16 OpID is only provided for those organizations that wish to use their E.212 network ID with 802.16, or may be required by regulation to do so. Organizations should check with their regulatory authorities as to whether they are required to use their current E.212 MCC-MNC pair to identify their networks using 802.16 standards. Any organization may obtain 802.16-specific OpID(s) from the IEEE Registration Authority, subject to the general terms & conditions covering application.

The OpID is assigned for worldwide use.

An OpID allocated by the IEEE Registration Authority is assigned to a single applicant. The assignee is guaranteed that the same number is not assigned to any other entity. Furthermore, the set of OpIDs that are assigned is disjoint from the set of OpIDs that may be derived from an E.212 MCC-MNC. The IEEE Registration Authority does not guarantee the MCC-MNC pair is unique. However, if all operators respect the rules for generating OpIDs and make use of unique MCC-MNC pairs, the OpID will be unique, since an OpID cannot be derived from two different E.212 MCC-MNC assignments. Any OpID selected from the Public OpID Pool is not guaranteed to be unique, as two operators may coincidently choose the same OpID. An operator choosing an OpID from the Public Pool must assess the consequences of another operator choosing the same OpID. For operators of a home or small enterprise network, the consequences may be insignificant, and choosing an operator ID from the public pool is a viable option.

The 802.16 standard requires the use of the OpID, as allocated by the IEEE Registration Authority. Failure to populate the a BS with an appropriate OpID will result in non-standard deployment and non-standard results. The value of the OpID field in new equipment is manufacturer-specific and should be verified by the operator.

A network OpID may be selected from the Public OpID Pool. Although such an OpID is not guaranteed to be globally unique, it will not cause mis-operation of any 802.16 SS/MS within its coverage or interference zones. Base stations in networks offering public service must use a globally unique OpID. Operators of base stations or networks using the Public OpID Pool should utilize appropriate access security techniques.

Although the total range of values is large, calculations of the probability of duplication in making a selection of truly random values from the full range yield the following results:

Within 10 random selections, there is a probability of duplication of 0.18%
With 23 random selections, there is a probability of duplication of 1%.
There is a 10% probability of duplication within a selection of 72 numbers;
There is a 50% probability of duplication within a selection of 185 numbers;
There is a 99% probability of duplication within a selection of 476 numbers.

From this it may be concluded that there is, for example, a 10% chance that mis-operation due to OpID duplication may occur if there are 72 (otherwise identical) base stations closely located such that their associated MSs may see signals from all the other BSs.

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