You can configure the NetScaler appliance to direct requests to a backup virtual server in the event that the primary load balancing virtual server is DOWN or unavailable. The backup virtual server is a proxy and is transparent to the client. The appliance can also send a notification message to the client regarding the site outage.

You can configure a backup load balancing virtual server when you create it, or you can change the optional parameters of an existing virtual server. You can also configure a backup virtual server for an existing backup virtual server, thus creating cascading backup virtual servers. The maximum depth of cascading backup virtual servers is 10.

If you have multiple virtual servers that connect to two servers, you have a choice for what happens if the primary virtual server goes DOWN and then comes back up. The default behavior is for the primary virtual server to resume its role as primary. However, you may want to configure the backup virtual server to remain in control in the event that it takes over. For example, you may want to sync updates on the backup virtual server to the primary virtual server and then manually force the original primary server to resume its role. In this case, you can designate the backup virtual server to remain in control in the event that the primary virtual server goes DOWN and then comes back up.

You can configure a redirect URL on the primary load balancing virtual server as a fallback for when both the primary and the backup virtual servers are DOWN or have reached their threshold for handling requests. When services bound to virtual servers are OUT OF SERVICE, the appliance uses the redirect URL.

Note: If a load balancing virtual server is configured with both a backup virtual server and a redirect URL, the backup virtual server takes precedence over the redirect URL. A redirect is used only when the primary and backup virtual servers are down.

To set a backup virtual server by using the command line interface

At the command prompt, type:

set lb vserver <vServerName> -backupVserver <BackupVServerName> -disablePrimaryOnDown

Example

set lb vserver Vserver-LB-1 -backupVserver Vserver-LB-2 -disablePrimaryOnDown

To set a backup virtual server by using the configuration utility

1. Navigate to Traffic Management > Load Balancing > Virtual Servers, and open the virtual server.
2. In Advanced Settings, click Protection, and select a backup virtual server.
3. If you want the backup virtual server to remain in control until you manually enable the primary virtual server even if the primary virtual server comes back up, select Disable Primary When Down.

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