Hyper-V MAC Addresses Duplication or Collison

November 25, 2011November 25, 2011 Samir Farhat Hyper-V Hyper-V MAC, Hyper-V MAC collison, Hyper-V management, Hyper-V networking

Networking in Hyper-V is one of the main feature in a virtual infrastructure.

like physical dimension, for each virtual machine ( for each virtual NIC) assigned a MAC address (classic and logic networking).

The question is:

– How these MAC addresses are created ?

– How these MAC addresses are assigned to Virtual machines ?

– How can i avoid MAC addresses collision ?

– Static Mac addresses or Dynamic MAC addresses ?

John Howard -MSFT has written an excellent blog about how MAC addresses are generated and assigned in Hyper-V.

http://blogs.technet.com/b/jhoward/archive/2008/07/15/hyper-v-mac-address-allocation-and-apparent-network-issues-mac-collisions-can-cause.aspx

What can we learn from John:

1- MAC addresses are generated based on the Microsoft IEEE Organizationally Unique Identifier 00-15-5D and the last 16 bytes from the Host IP address: MAC address RANGE = 00-15-5D-(Hex(last 16 bytes of Host IP))+00 to 00-15-5D-(Hex(last 16 bytes of Host IP))+ff

Example:

If my host IP address is 192.168.20.1, the last 16 bytes are 20.1, in hex 14-01 and the MAC address range is [00-15-5D-14-01-00;00-15-5D-14-01-ff]

2- How MAC addresses are assigned: Each new created virtual machine NIC receives the next available MAC address.

Example: (NIC1, 00-15-5D-14-01-00), (NIC1, 00-15-5D-14-01-01), (NIC1, 00-15-5D-14-01-02) …

3– If MAC addresses range is saturated: Virtual machine with virtual NIC will be unable to boot

4- Dynamic or Fixed MAC range:

In production environment, it’s recommended to fix your MAC addresses range. This will simplifie management, tracking, avoid collision.
If your environment is large, and it’s possible to have two hosts with the same last 16 bytes, think to fix your MAC addresses range
Try to manage your Virtual environment with SCVMM, it automatically avoid MAC collision, it has global view of all your hosts.

Hyper-V console alternative

November 25, 2011November 25, 2011 Samir Farhat Hyper-V Hyper-V connection, Hyper-V console, Hyper-V console alternative, Hyper-V management, Hyper-V remote

Using the Hyper-V console may be sometimes impossible or dificult to realize. The most cases are when you are facing a Windows server 2008 R2 core edition or a Windows Hyper-V server 2008 R2.

Others possibilities are when you are unable to open the Hyper-V console.

Regardless what is your reason, an Hyper-V console alternative exists, and for FREE

5nine Manager for Hyper-V provides an EASY_Monitoring for Hyper-V and a local Graphical User Interface to Microsoft Hyper-V R2 server. It supports Hyper-V technology on Full and Core installations of Windows Server 2008 R2, as well as on Microsoft Hyper-V Server 2008 R2, which is the Microsoft’s standalone FREE Hypervisor! You can use it when Microsoft SC VMM, or even Hyper-V Manager are not available for Core or Free versions of Server 2008 R2. It also provides Value-Add functions, such as advanced network bindings, performance monitoring, and a hardware profiling for all flavors of Server 2008 and Free/Core Hyper-V installations.

Download 5nine (You must register before downloading it, but for free too )