This article describes how to configure redirect URL on ADC virtual server when virtual server is not available.

Background

You can configure an HTTP or HTTPS virtual server with a redirect URL. This URL is sent as a response to the client HTTP or HTTPS request if the virtual server is not available. The common usage of this option is to direct the client to a customized "Site Down" web page or to an external backup website. However, this feature is not applicable for the non-HTTP or non-HTTPS protocols.

If the state of the virtual server is DOWN or DISABLED, then the ADC appliance responds to HTTP(S) requests with the HTTP/1.x 302 – Object Moved response code and the configured redirect URL specified in the Location header of the HTTP response. The exact URL specified in the response depends on the following configuration options:

• If the configured redirect URL only contains the domain name, such as http://www.sample1.example.com, the redirect URL specified in the HTTP response appends the Uniform Resource Identifier (URI) specified in the HTTP request to the configured domain name. For example, if the request contains the GET http://www.sample2.example.com/images/site_nav.gif header, then the Location header in the redirect response specifies the Location: http://www.sample1.example.com/images/site_nav.gif header.
  Note: The domain names in the request and response can differ. In this article, the two domains are referred to as sample1.example.com and sample2.example.com to explain the concept.

• If the configured redirect URL contains a complete path, then the redirect response specifies the complete configured URL, irrespective of the URI in the request. For example, the following are such URLs:
  Requested URL - http://www.redirect.com/en/index.html
  Redirect URL - http://www.redirect.com/en/site_down.html

The following table illustrates the preceding configuration options:

Note: It is worth noting that when configuring a redirect URL, the http://example.com URL is not the same as the http://example.com/ URL because the latter contains the complete path to the web root, /.

Instructions

Please refer to the docs link: https://docs.citrix.com/en-us/citrix-adc/13/load-balancing/load-balancing-protect-configuration/redirect-alternate-url.html

Citrix Documentation - Redirecting Client Requests to an Alternate URL
CTX117344 - How to Secure Web Access by Redirecting HTTP URLs to HTTPS URLs on a NetScaler Appliance Using Content Switching
CTX121490 - How to Redirect an HTTP Request to an HTTPS Server and Retain the Path and Query of the URL Using Responder Feature
CTX120664 - How to Use the Responder Feature of the NetScaler Appliance for URL Redirects