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Setting Multiple Isolation Response Addresses for VMware High Availability (1002117)

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In VirtualCenter Server 2.0.2 and above, you can specify more than one isolation response address for VMware High Availability (HA). The use of multiple isolation response addresses offers VMware HA a potentially more accurate picture of the network connectivity of a host. There may be situations in which a single isolation address would indicate that a host is in a state of complete isolation from the network, but access to additional isolation addresses would show that only a partial network failure has occurred.


Multiple isolation response addresses can be specified using the das.isolationaddress0 through das.isolationaddress9 options.
To specify the values for these options in Virtual Infrastructure Client:
  1. Select the HA cluster.
  2. On the Summary tab, click Edit Settings.
  3. In the Settings dialog, select VMware HA.
  4. Click Advanced Options.
  5. In the Advanced Options (HA) dialog, enter the option name and the corresponding value:

    • Option: das.isolationaddress0
    • Value: A valid IP address other than the default gateway address

      Similarly, you can set more isolation response addresses using das.isolationaddress1 through das.isolationaddress9.

  6. In the Advanced Options (HA) dialog box, set this option:
    • Option: das.usedefaultisolationaddress
    • Value: false

      • You must set this option if you are setting multiple isolation response addresses.
      • Additionally you should configure das.usedefaultisolationaddress to false when the default gateway is a device which cannot be pinged.

  7. Click OK.
  8. Click OK.
  9. Edit settings for the cluster again.
  10. Disable HA and click OK.
  11. Edit settings again.
  12. Enable HA and click OK.

At the time of VMware HA configuration, if none of the specified addresses can be reached, the configuration operation fails. If only a subset of the specified isolation addresses cannot be reached, then the configuration operation succeeds, but a configuration issue is displayed for the cluster and the cluster becomes yellow. The configuration issue identifies the isolation response addresses that could not be reached.

Although VMware HA supports a maximum of 10 isolation response addresses, in most cases one or two isolation response addresses should be sufficient. Also, the das.isolationaddress option formerly used to set a single isolation response address is still supported.

Note: If you specify multiple isolation response addresses, VMware recommends that you ensure the correct operation of VMware HA by:
  • Use the default gateway address and other reliable addresses physically close to the hosts in the cluster.
  • Ensure a corresponding isolation address is setup for each service console network that has been created on the ESX Server.
  • Change the default failure detection time to 20 seconds or greater. To change the default failure detection time:

    1. Select the HA cluster.
    2. On the Summary tab, click Edit Settings.
    3. In the Settings dialog, select VMware HA.
    4. Click Advanced Options.
    5. In the Advanced Options (HA) dialog, enter the option name and the corresponding value:

      • Option: das.failuredetectiontime
      • Value: A value in milliseconds that represents the timeout value (20 seconds = 20000 milliseconds)

    6. Click OK.
    7. Click OK


  • das.failuredetectiontime does not need to be increased when multiple das.isolationaddress options are specified as the pings occur in parallel.
  • das.failuredetectiontime is no longer supported in vCenter Server 5.0. For more information, see vSphere HA Advanced Attributes

For information on VMware HA best practices, see Best practices and advanced features for VMware High Availability (1002080).

For further details, see the vSphere Availability guide.

Additional Information

For translated versions of this article, see:

Update History

01/28/2011 - Added vCenter Server 4.x to Products 06/18/2012 - Added two additional notes in Solution 06/18/2012 - Changed 1-10 to 0-9 for das.isolationaddress. 07/03/2012 - Added note that das.failuredetectiontime is no longer support in vCenter Server 5.0

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