In order to successfully set up Symantec Protection for SharePoint Servers (SPSS) 6.0.6 and later to run in failover mode for high-availabity and disaster recovery, the SPSS configuration file “Symantec.Sharepoint.SPSSService.exe.config” located in “<Install Dir>:\Program Files\Symantec\SharePoint” must be changed. 

To change the configuration file:

1.    Stop the SPSS service.
2.    Open the configuration file to edit its content.
3.    Search for the key “SPSSConfigDB”
4.    Edit the value for the above mentioned key and add a new connection string parameter to change the connection behaviour as shown below

<add key="SPSSConfigDB" value="Data Source=PTD9312;Initial Catalog=SPSSDB;Integrated Security=SSPI; MultiSubnetFailover=True" />

5.    Save the configuration file.
6.    Start the SPSS service.

Fore more information regarding the MultiSubnetFailover parameter, please see the following documentation from Microsoft:

SqlClient Support for High Availability, Disaster Recovery

Connection Timeouts in Multi-subnet Availability Group