Conclusion If changing a wireless MAC “fails,” the most common cause is an invalid first octet (multicast bit set or LAA unset) or driver/network-manager/firmware preventing spoofing. Use a locally administered unicast first octet (like 02) and follow the platform steps above; if it still fails, the adapter driver likely blocks MAC spoofing.

Do not guess. Use these valid first octets for local MAC addresses:

If your MAC address change is failing or reverting, you must set the first octet of the new address to a value that identifies it as Locally Administered The Easiest Fix: Set the first octet to 02:XX:XX:XX:XX:XX Other Valid Options: The first octet can also end in Cisco Community Why the First Octet Matters

That’s an interesting failure case — and a surprisingly common one for people experimenting with MAC spoofing on Wi-Fi.

: Some adapters are hardware-locked and will not allow changes regardless of the prefix. How to Fix It