Stacking providers are external hosts managed by the Content Filtering (CF) performing various traffic analysis and filtering (for example, virus and spam filtering). These hosts can be listed as Stacking providers, and easily referenced from multiple service definitions.

A Stacking provider includes the IPv4 or unix socket of the host performing the analysis of the traffic. If multiple hosts are set in a single policy, they will be used in a fail-over fashion, that is, if the first host is down, the traffic will be directed to the second one for analysis, and so on.

Figure 6.73. Creating a new Stacking Provider through IPv4

Figure 6.74. Creating a new Stacking Provider through domain socket

To specify an IPv4 socket, the IP address and port of the host has to be specified. To specify a unix domain socket, the full path (including the actual filename) has to be provided.

For details about CF and the configuration and use of stacking providers, see Chapter 14, Virus and content filtering using CF.