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Set up a custom domain by configuring your own CDN

There are two ways to configure your own CDN:

  • use Cloud Foundry commands
  • amend HTTP request headers

You should use these methods if you need access to features that are not provided by the cdn-route service. The cdn-route section has information on the features provided by the service.

There are many different CDNs available. Contact us at gov-uk-paas-support@digital.cabinet-office.gov.uk to discuss best practice for configuring your CDN to work with the PaaS.

Use Cloud Foundry commands

Set up connection between custom domain and CDN

  1. Register your custom domain with a domain name registrar.

  2. Choose a CDN provider.

  3. Set up the connection between your custom domain and the CDN provider, following the CDN provider’s instructions.

Configure your custom domain in Cloud Foundry

  1. Target the space your application is running in:

    cf target -o ORGNAME -s SPACENAME
    
  2. Create a domain in your organisation (replace ORGNAME with your org name, and replace example.com with your domain):

    cf create-domain ORGNAME example.com
    
  3. Map the subdomain route to your application:

    cf map-route APPNAME example.com --hostname www
    

Configure your CDN

Configure your CDN to forward HTTPS traffic to the PaaS at your app domain, providing a HTTP Host header for your custom domain (for example Host: www.example.com).

For example, if your app is hosted in the London region, your app domain is london.cloudapps.digital. When your CDN connects to the london.cloudapps.digital server, the server will present a TLS certificate valid only for london.cloudapps.digital and *.london.cloudapps.digital. Your CDN must accept this certificate.

Amend HTTP request headers

Set up connection between custom domain and CDN

  1. Register your custom domain with a domain name registrar.

  2. Choose a CDN provider.

  3. Set up the connection between your custom domain and the CDN provider, following the CDN provider’s instructions.

Configure your CDN

  1. Configure your CDN to forward HTTPS requests from your custom domain to the PaaS at the YOURAPP.APP_DOMAIN domain.

  2. Configure your CDN to amend the HTTP requests when it forwards those requests by:

  • changing the HTTPS request Host header from your custom domain to your app’s domain (for example if your app is hosted in the London region, change Host: www.example.com to Host: YOURAPP.london.cloudapps.digital)

  • adding a X-Forwarded-Host HTTP header containing your custom domain to the HTTPS request (for example X-Forwarded-Host: www.example.com)

In the above example, the HTTP request header will change from:

GET / HTTP/1.1
Host: www.example.com

to:

GET / HTTP/1.1
Host: YOURAPP.london.cloudapps.digital
X-Forwarded-Host: www.example.com

Configure your app

Configure your app to obtain its hostname from the X-Forwarded-Host HTTP header.