Managing Hyper-V dynamic MAC address pool

By default, the default value of dynamic MAC addresses is 256 in all versions of Hyper-V servers. 

How come the default is 256?

According to KB2804678, Hyper-V generates the MAC address by the following algorithm.

• The first three octets (aa-bb-cc) are Microsoft's IEEE organizationally Unique Identifier, 00:15:5D (which is common on all Hyper-V hosts).
• The next two octets (dd-ee) are derived from the last two octets of the server's IP address.
• The last octet (ff) is automatically generated from the range 0x0 - 0xFF.

Because the last octet is an 8-bit value, there is a default limit of 256 possible MAC addresses.

1. To increase the MAC address pool, click "Virtual Switch Manager" in "Hyper-V Manager".

2. Next to "MAC Address Range".

Administrators can modify the MAC address pool from here.

3. Or, Administrators can assign a static MAC address for a virtual machine in Network Adapter.

More information:

Windows Hyper-V server has a default limit of 256 dynamic MAC addresses

This posting is provided “AS IS” with no warranties, and confers no rights!