PerimeterX Fastly Enforcer is a Varnish Configuration Language (VCL) based module that runs on Fastly's edge, detects and blocks unwanted traffic from reaching the origin. When the PerimeterX's Enforcer determines that a request is coming from a non-human source, the request is handled according to the configurations. Protecting your website with PerimeterX's Fastly VCL integration supports both regular service and service using shielding.

Fastly Limitations

  • Body Size: 8196

  • Number of Headers: ~85

  • Fastly allows a total of 3 Varnish restarts in order to prevent endless looping

  • VCL File Size: 64k

  • Origins Per Service: Default 5
    The PerimeterX VCL module uses more Origins per Service than the default.
    Exceeding this limit results in the error Exceeding max_backends.

    To increase the number of Origins per Server, you must contact Fastly Support to inform them that the additional Origins per Service are for the PerimeterX VCL module. Fastly will increase the number of Origins per Service available to you.

For a full list of Fastly limitations, see the Fastly documentation

Note: Your servers must allow requests originating only from Fastly nodes.