How Can People Hardware Ban Someone or a NIC MAC Address on a Private Network?

Many individuals often wonder if the MAC address is exclusive to private networks and how one can ban someone or block their network interface card (NIC) MAC address. This article aims to clarify these common misconceptions and provide a comprehensive understanding.

Understanding MAC Addresses and Private Networks

A MAC address is a unique identifier assigned to network interfaces for communications on a network segment. It is not limited to private networks but is commonly used within such environments for various security measures. Privately-owned companies have their own data networks, which they can manage and control as they see fit.

The confusion often stems from the limited visibility and accessibility of MAC addresses outside a local network. While a MAC address is indeed a physical hardware identifier, it plays a crucial role in network security and management.

Banning a Device on a Private Network

When you ban a MAC address on a private network, such as a Wi-Fi or Ethernet port, you are effectively preventing that specific device from accessing the network. For example, if someone is using your Wi-Fi and you wish to block them, you can blacklist their MAC address. This action is typically performed at the Wi-Fi router level.

However, it's important to note that MAC addresses can be spoofed. An attacker could easily change their MAC address to evade the ban. Therefore, while MAC address bans are a useful security measure, they should be supplemented with other security protocols.

What You Can Actually Ban

When you ban a NIC MAC address at the Wi-Fi router level, you are blocking the device from making a connection to the network. The router will refuse to establish a link with the device based on the MAC address specified in its blacklisted list. This is a local network-level measure and is not feasible for large-scale networks or the Internet as a whole.

Moreover, the MAC address is not visible outside of a local network. This means that a network administrator can only effectively ban a device within their controlled environment. However, there are some potential corner cases where a remote service might use a device's MAC address as part of its security measures. For instance, some services may use MAC addresses to verify authorized systems or prevent unauthorized access.

IPv6 and MAC Addresses

It's worth noting that in some cases, the MAC address is embedded in the client's IPv6 address, as specified in RFC 7217. Although this method is deprecated, it is still possible that some gear is currently supporting this functionality. While this method can be used for verification purposes, it is far from being a common practice in modern network setups.

Conclusion

MAC addresses are essential identifiers in the world of network security and management. While they are typically used on private networks, they can also be employed to ban devices at the local network level. However, due to the limitations of local network visibility, true global bans based solely on MAC addresses are not possible without additional measures or services.