Oracle® VM Server for SPARC 3.2 Administration Guide

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Updated: May 2015

Duplicate MAC Address Detection

To prevent the same MAC address from being allocated to different devices, the Logical Domains Manager checks with other Logical Domains Managers on other systems by sending a multicast message over the control domain's default network interface, including the address that the Logical Domains Manager wants to assign to the device. The Logical Domains Manager attempting to assign the MAC address waits for one second for a response. If a different device on another Oracle VM Server for SPARC-enabled system has already been assigned that MAC address, the Logical Domains Manager on that system sends a response containing the MAC address in question. If the requesting Logical Domains Manager receives a response, it notes the chosen MAC address has already been allocated, chooses another, and iterates.

By default, these multicast messages are sent only to other managers on the same subnet. The default time-to-live (TTL) is 1. The TTL can be configured using the Service Management Facilities (SMF) property ldmd/hops.

    Each Logical Domains Manager is responsible for the following:

  • Listening for multicast messages

  • Keeping track of MAC addresses assigned to its domains

  • Looking for duplicates

  • Responding so that duplicates do not occur

If the Logical Domains Manager on a system is shut down for any reason, duplicate MAC addresses could occur while the Logical Domains Manager is down.

Automatic MAC allocation occurs at the time the logical domain or network device is created and persists until the device or the logical domain is removed.

Note - A detection check for duplicate MAC addresses is performed when the logical domain or network device is created, and the logical domain is started.