Switching Over and Switching Back › Setting High Availability Properties › Understanding High Availability Properties › Network Traffic Redirection

Network Traffic Redirection

There are three redirection methods:

• Move IP
• Redirect DNS
• Switch Computer Name
• Switch Computer Alias

You may also specify User-defined scripts for each server type.

The three redirection methods can be used according to the following table:

Note: For computer alias names, Arcserve RHA supports UNC access.

After a switchover takes place, the A-records of Master and Replica servers are changed on the DNS server, depending on which Network Redirection Methods you select. The following table shows what network redirection methods impact the DNS A-record.

• If the Network Redirection method is MoveIP, the DNS A-record is not impacted.
• If the Network Redirection is DNS redirection, the A-record Master redirects to the Replica IP after switchover, while the Replica A-record doesn't change.
• If the Network Redirection is Switch Computer Name, the Master A-record changes to Master-RHA after switchover, and the Replica A-record changes to Master.
• If the network redirections are DNS redirection and switch computer name, the result is same as only DNS redirection.

If you want to keep the Replica A-Record, use the DNS Redirection method or DNS and Switch Computer Name methods.

Move IP

During switchover, the switchover IP(s) are released on the active host and added to the standby host. This redirection method is applicable only when both the Master server and the Replica server are on the same IP subnet.

Choosing Off or On affects the available options in the Check With property for a Send ping request. Refer to Is Alive.

Add IP/Mask

Enter IPs for the active computer that will be moved to the standby computer during switchover. The Master IP address defined in the Master Properties must be different than the IPs entered here.

To add IP/Mask

1. Click the tree entry: Click here to add new IP/Mask.

   The IP Address dialog appears.

2. Enter the relevant IP/Mask data in the dialog and click OK.

   A new entry is added to the list, and a new row opens for another IP/Mask. Enter as many entries as you require.

   Notes:

   • The Master IP address on the Properties tab under Host Connection (the Master IP that was entered in the Scenario Creation Wizard), must NOT be one of the IPs included in this list.
   • If the Move IP or the Redirect DNS property is set to On, Arcserve RHA turns off the dynamic DNS registration for the Master. (The checkbox, Register this connection's addresses in DNS in the Advanced TCP/IP Settings dialog is cleared).

Redirect DNS

During the switchover, the A-record of the Master Server will be updated. This redirection option is applicable when the Master and the Replica are located on a different IP subnet or on the same subnet.

If the Move IP or the Redirect DNS property is set to On, Arcserve RHA turns off the dynamic DNS registration for the Master. (The checkbox, Register this connection's addresses in DNS in the Advanced TCP/IP Settings dialog, is cleared).

DNS Server IPs

Enter IPs of DNS servers to update. Arcserve RHA tries to update all servers listed. However, switchover is considered successful even if only one update is successful.

To enter the value, click the tree entry: Click here to add new IP.

DNS TTL

Enter number of seconds for DNS Time-To-Live. This value is changed in the DNS Server for the A-record that is updated.

Active Directory Integrated

Specify if DNS is an Active Directory Integrated. If the Master DNS is on a Windows platform and integrated with Active Directory, set this option to On.

DNS Key Filename (full path)

Enter the full path of the file containing the DNS secure key. This field appears only when AD Integrated is Off.

Master/Replica IPs in DNS

Enter the Master/Replica IPs in its DNS server.

The Master's DNS record is updated during every switchover: in the switchover from Master to Replica, the addresses in the Master's DNS record are replaced by the addresses of the Replica. In the switch back from Replica to Master, the addresses are restored to the original values.

To enter the value, click the tree entry: Click here to add new IP.

Switch Computer Name

This redirection option is applicable when you use NetBIOS name resolution for your connections with the Master. If the hostname and the NetBIOS name are not the same, this option cannot be used.

During the switchover, the Replica computer is renamed to the Master computer name and the Master computer is renamed to a temporary name (if the Master server is alive). During the switchback, the names are restored. Both the hostname and the NetBIOS name are changed. When Switch Computer Name redirection is enabled in the Active Directory environment, the Master and Replica servers must be members of the same domain or trusted domain.

Important! If you will be redirecting File Shares, in which clients connect to via the Master server name, Switch Computer Name must be enabled. For example, if the Master server's name is fs01 and clients connect to \\fs01\sharename or \\fs01.domain.com\sharename, then you must use the Switch Computer Name method. We also recommend enabling one other method. The most common method is to use both DNS Redirection and Switch Computer Name.

When you use the Switch Computer Name redirection method on Windows 2008 and Windows 2008 R2 systems, a reboot is required after switchover and switchback. You cannot run a reverse scenario until the system is restarted because the computer name does not take effect until the reboot completes. We recommend setting the Reboot After Switchover and Switchback property to On when using this method.

Master Computer Name

NetBIOS name of the Master computer. This name cannot be modified here.

Replica Computer Name

NetBIOS name of the Replica computer. This name cannot be modified here.

Reboot after Switchover and Switchback

After a switchover and a switchback, if this option is set to On, both Master and Replica computers are rebooted.

Use Computer Name Alias

After a switchover, the Computer Name of the original Replica will not be changed. Instead, the Replica will use the Master hostname as the Alias, and therefore it will not have to reboot. If you set this option to On, we recommend you set the Redirect DNS property to On.

User Defined Scripts

This option allows the standard redirection methods to be enhanced or replaced by actions that are invoked by user-defined scripts.

Important! When using scripts, each script must reside in the same path and with the same name on both the Master and the Replica.

Active to Standby Redirection Script

• Script Name

  Enter the name and full path of script to be run on the active computer, if it is alive, in order to redirect clients to the standby computer or release network resources on active host.

• Arguments

  Arguments to be passed to the script specified in the previous property. Argument values must be static.

Note: The Active to Standby Redirection Script is also automatically executed when the HA scenario starts running. At this stage, the script runs on the standby Replica.

Standby to Active Redirection Script

• Script Name

  Enter the name and full path of script to be run on the standby host, in order to redirect clients to it or add network resource.

• Arguments

  Arguments to be passed to the script specified in the previous property. Argument values must be static.

Identify Network Traffic Direction Script

Required to fully support custom redirection methods. The custom scripts entered here are used to identify the active server. The Engine assumes that:

• If the script was executed on the host is returning 0, then the host is active (has all network resources on it or users directed to this host)
• If the script is returning a non-zero value, then the host is inactive (all or some of the network resources are absent, or users are not directed to this host).

• Script Name

  Enter the name and full path of script to be run. This script determines if the Forward or Backward scenario will run when the scenario is started. The script runs on both Master and Replica: the one that returns zero is active. If both return the same value, a conflict is reported.

• Arguments

  Arguments to be passed to the script specified in the previous property. Argument values must be static.

Switch Computer Alias

During switchover, the alias name is released from the active host and added to the standby host.

Both NetBIOS and DNS CNAME alias names are supported. To add NetBIOS alias names, create a Multi-String value named OptionalNames with Data as <aliasnames> in the following registry key and restart the Server service.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\LanmanServer\Parameters

Note: When the master server is a workgroup server, then the switchover by DNS alias name cannot be supported. The reason is that the user of the workgroup server does not have the privileges to access the DNS information.

Alias Name

Enter the alias name of the active host that is moved to the standby host during switchover.

Update/Add/Delete

By default, alias name is auto configured when the HA scenario is created. You can add or delete all or the selected aliases.

After the scenario is created, you can also add a new alias in your environment. To enable this new alias, click the refresh button and reload the HA properties.