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Non-Microsoft DNS

If you are using a non-Microsoft DNS server (such as Unix) or if you are in a non-domain configuration (such as a workgroup), when Double-Take Availability failover occurs, DNS is not automatically updated. If the end-users use DNS to resolve server names and the source IP address was not failed over to the target, additional DNS updates will be required because the host records for the source will remain intact after failover. You can automate this process by scripting the DNS updates in the failover and failback scripts.

If you are protecting an application, you can configure the Application Manager not to check for Microsoft DNS or you can start the Application Manager from the command line and specify the /altdns option after your application switch.

For other workload protections, one option is to use a BIND DNS client for DNS scripting. The following steps provide an example of how you can use a BIND DNS client for DNS failover and failback scripting. You may need to modify this example to fit your environment.

  1. Go to www.isc.org and download the appropriate BIND DNS client.
  2. Install the BIND client on the target server.
  3. Set a PATH statement for the BIND directory to ensure that it runs every time the executable is called.
  4. Create a failover script file in the Double-Take Availability directory.
  5. Add the following line to the failover script file, substituting your Double-Take Availability directory for install_location.

    6. nsupdate.exe "c:\install_location\dnsover.txt"

  6. Save the failover script file.
  7. Create a text file, called dnsover.txt in the Double-Take Availability directory.
  8. Add the following lines to the dnsover.txt file, substituting your source name, fully-qualified domain name, target name, and target IP address as appropriate.

    9. update delete source_server_name.fully_qualified_domain_name.com A

    update add target_server_name.fully_qualified_domain_name.com 86400 A target_server_IP_address

    send

  9. Save the dnsover.txt file.
  10. Create a failback script file in the Double-Take Availability directory.
  11. Add the following line to the failback script file, substituting your Double-Take Availability directory for install_location.

    12. nsupdate.exe "c:\install_location\dnsback.txt"
  12. Save the failback script file.
  13. Create a text file, called dnsback.txt in the Double-Take Availability directory.
  14. Add the following lines to the dnsback.txt file, substituting your target name, fully-qualified domain name, source name, and source IP address as appropriate.

    15. update delete target_server_name.fully_qualified_domain_name.com A

    update add source_server_name.fully_qualified_domain_name.com 86400 A source_server_IP_address

    send

  15. Save the dnsback.txt file.
  16. Change the Double-Take service on the target server to a domain account that has rights to modify BIND DNS. Stop and start the service to have it take effect.