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Network Isolation capability can fail if the SCVMM Server Global Static MAC address range assigns Multicast MAC addresses to emulated NICs

Symptoms

Network Isolation capabilty fails with the following error:

TF273002: The network agent encountered an error and skipped one or more commands. Stop and restart the environment. Additional information: (Failed to find a DHCP enabled adapter with a valid IPv4 address OSCode: 0)

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Cause


Emulated NICs in network isolated environments are assigned MAC addresses from the SCVMM Server's global static MAC address range.

Let us say that the SCVMM Server's global static MAC address range is set to: 99-99-99-00-00-00 – 99-99-99-00-00-FF

This range is a multicast MAC address range. Ethernet uses the low-order bit of the high-order octet to distinguish conventional unicast addresses from multicast addresses. A unicast would have this bit set to ZERO (0), whereas a multicast would be set to ONE (1). So if the second byte of a MAC address is odd (IE 01, 03, 05,..99), the least significant bit is set to 1, which means it is a multicast address.


Hyper-V or SCVMM servers do not allow Multicast MAC addresses to be assigned to NICs inside the virtual machines.

The above range would therefore have been valid if the first octet was set to 98, 96,94 etc.

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Resolution

Ensure that the second byte of the first octet in the SCVMM server's global static address range is even or 0. For example, the following MAC address range is a valid: 98-99-99-00-00-00 – 98-99-99-00-00-FF.

To set the MAC address range, in Administration view of the VMM Administrator Console, expand the Networking node, and then click Global static MAC address range. For more information, see How to Set the Static MAC Address Range for Virtual Network Devices.

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More Information

For additional information, see the following:

http://standards.ieee.org/develop/regauth/tut/macgrp.pdf

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Keywords: kb

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Article Info
Article ID : 2758965
Revision : 1
Created on : 1/7/2017
Published on : 9/24/2012
Exists online : False
Views : 62