Citrix ADC

Responder

Warning

Filter features using classic policies are deprecated and as an alternative, Citrix recommends you to use the rewrite and responder features with advanced policy infrastructure.

Today’s complex Web configurations often require different responses for HTTP requests. When users request a webpage, you might provide a different page depending on user geographical location, browser specification, or languages the browser accepts and the order of preference. You might want to drop a connection if the request is coming from an IP range that has DDoS attacks or initiating hacking attempts.

Responder supports protocols such as TCP, DNS (UDP), and HTTP. With responder enabled on your appliance, server responses are based on who sends the request, where it comes from, and other criteria with security and system management implications. The feature is simple and quick to use. By avoiding the invocation of more complex features, it reduces CPU cycles and time spent in handling requests that do not require complex processing.

For handling sensitive data such as financial information, if you want to ensure that the client uses a secure connection to browse a site, you can redirect the request to a secure connection by using https:// instead of http://.

To use the Responder feature, do the following;

  • Enable the Responder feature on the Citrix ADC.
  • Configure responder actions. The action can be to generate a custom response, redirect a request to a different webpage, or reset a connection.
  • Configure responder policies. The policy determines the requests (traffic) on which an action has to be taken.
  • Bind each policy to a bind point put it into effect. A bind point refers to an entity at which Citrix ADC examines the traffic to see if it matches a policy. For example, a bind point can be a load balancing virtual server.

You can specify a default action for requests that do not match any policy, and you can bypass the safety check for actions that would otherwise generate error messages.

The Rewrite feature of Citrix ADC helps in rewriting some information in the requests or responses handled by Citrix ADC. The following section shows some differences between the two features.

Comparison between Rewrite and Responder options

The main difference between the rewrite feature and the responder feature is as follows:

Responder cannot be used for response or server-based expressions. Responder can be used only for the following scenarios depending on client parameters:

  • Redirecting an HTTP request to new websites or webpages
  • Responding with some custom response
  • Dropping or resetting a connection at request level

If there is a responder policy, the Citrix ADC examines the request from the client, takes action according to the applicable policies, sends the response to the client, and closes the connection with the client.

If there is a rewrite policy, the Citrix ADC examines the request and forwards it to the server.

In general, it is recommended to use responder feature, if you want the appliance to reset or drop a connection based on a request-based parameter. Use responder to redirect traffic, or respond with custom messages. Use rewrite for manipulating data on HTTP requests and responses.

Responder