Working with hosts

To communicate with your origin servers, you can add and edit a host.

Before you begin

Be sure you learn about the web interface controls and how to work with services before you start working with your hosts.

Adding a host

To add a host, follow the steps below:

  1. Log in to the Fastly web interface.
  2. From the All services page, select the appropriate service. You can use the search box to search by ID, name, or domain.
  3. Click the Edit configuration button and then select the option to clone the active version. The Domains page appears.
  4. Click the Origins link. The Origins page appears.
  5. Click the Create a host button. The Hosts field appears.

    Create a host

  6. Fill out the Hosts field by entering the hostname or IP address of your origin server. Entering a hostname automatically enables Transport Layer Security (TLS) and assigns port 443. Entering an IP address disables TLS and assigns port 80.
  7. Click Add to add your host.

Editing a host

After you've created your host, you can edit the host's details by following the steps below:

  1. In the Hosts area, click the pencil icon next to the Host you want to edit. The Edit this host page appears.

    the Edit this host page

  2. Fill out the Edit this host fields as follows:

    • In the Name field, enter the name of your server (for example, My Origin Server). This name is displayed in the Fastly web interface.
    • In the Address field, enter the IP address (or hostname) of your origin server.

    See Understanding the difference between certificate hostname and SNI hostname values for more information about hostnames.

    Transport Layer Security (TLS)

  3. Fill out the Transport Layer Security (TLS) area as follows:

    • Leave the Enable TLS? default set to Yes if you want to enable TLS to secure the connection between Fastly and your origin. To enable TLS, a valid SSL certificate must be installed on your origin server and port 443 (or the specified port) must be open in the firewall. You can select No if you do not want to use TLS.
    • Leave the Verify certificate? default set to Yes if you want to verify the authenticity of the TLS certificate. Selecting No means the certificate will not be verified.

    • In the Certificate hostname field, enter the hostname associated with your TLS certificate. This value is matched against the certificate common name (CN) or a subject alternate name (SAN) depending on the certificate you were issued. See our guidance on understanding the difference between certificate hostname and SNI hostname values for additional details.
  4. Fill out the remaining Create a host fields as follows:

    • From the Shielding menu, optionally select a POP to enable the shielding feature. For more information, see our guide on shielding.
    • From the Health check menu, optionally select a health check for this origin server. For more information, see our guide on working with health checks.
    • From the Auto load balance menu, optionally select Yes to enable load balancing for this origin server. For more information, see our guide on load balancing.
    • If you enabled load balancing, enter a weight in the Weight field.
  5. Click the Advanced options link and decide which of the optional fields to change, if any:
    • In the Maximum connections field, optionally enter the maximum number of connections for your backend. The default limit is 200 connections per cache node to protect your origins from being overloaded.
    • In the Error threshold field, optionally enter the number of errors allowed before an origin is considered down.
    • In the Connection timeout field, optionally enter how long, in milliseconds, to wait for a connection timeout. The default is 1000 milliseconds.
    • In the First byte timeout field, optionally enter how long, in milliseconds, to wait for a first byte timeout. The default is 15000 milliseconds.
    • In the Between bytes timeout field, optionally enter how long, in milliseconds, to wait between bytes. The default is 10000 milliseconds.
  6. In the Override host field, optionally enter the hostname of your override Host header based on the origin you’re using. The value in this field will take precedence over anything you've set using the global override host configuration. To see example Host headers for third-party services, refer to our developer documentation on overriding the Host header.

  7. Click the Update button. The new override host appears under the Show all details field of the Override host section and a code block is added to the origin definition in your VCL that will look similar to the following:

    Backend F_Host_1 {
       .host = "..."; # IP or hostname
       .host_header = "";
       .always_use_host_header = true;
  8. Click the Activate button to deploy your configuration changes.

And that's all you need to do. Everything else is optional, but just in case you'd like to set them, we've included the information below.

Setting the TLS hostname

Normally we check the server certificate against the hostname portion of the address for your origin entered in the Create a host window. Checking the certificate is done by using the value of the Certificate Hostname field in your origin TLS settings. To have Fastly verify the certificate using a different hostname, specify it via the SNI Hostname field under Advanced options.

This information also gets sent to the server in the TLS handshake. If you are using Server Name Indication (SNI) to put multiple certificates on your origin, specifying it in the SNI Hostname field will select which one is used.

Understanding the difference between certificate hostname and SNI hostname values

The following explains the difference between a certificate and SNI hostname value:

The certificate hostname (ssl_cert_hostname). This hostname validates the certificate at origin. It is always required. This value should match the certificate common name (CN) or an available subject alternate name (SAN). It displays as ssl_cert_hostname in VCL. This doesn't affect the SNI certification. You can set this value in Certificate hostname field of the TLS options page.

The SNI hostname (ssl_sni_hostname). This hostname determines which certificate should be used for the TLS handshake. SNI is generally only required when your origin is using shared hosting, such as Amazon S3, or when you use multiple certificates at your origin. SNI allows the origin server to know which certificate to use for the connection. This value displays as ssl_sni_hostname in VCL. This doesn't affect the certificate validation.

The table below shows you what happens when you set the Certificate and SNI hostname values in the TLS settings:

If Certificate hostname contains… and SNI hostname contains… then the Certificate Validation value will be… and the SNI value will be… nothing nothing

About the ssl_hostname value (deprecated). The ssl_hostname value has been deprecated and replaced with ssl_cert_hostname and ssl_sni_hostname. Use these two values instead.

Using a wildcard certificate

If you're using a wildcard certificate, you can use any SNI hostname that matches the wildcard certificate. The SNI hostname must be a fully-qualified domain name (FQDN), per RFC 6066.

The table below shows a variety of possible combinations of certificate and SNI hostnames that could be used with a wildcard certificate for *

Certificate hostname SNI hostname

If you set the certificate hostname to *, Fastly will treat it as a literal.

Specifying a TLS CA certificate

If you're using a certificate that is either self-signed or signed by a certification authority (CA) not commonly recognized by major browsers (and unlikely to be in the Ubuntu bundle that we use), you can provide the certificate in PEM format via the TLS CA certificate field. The PEM format looks like this:

a PEM form certificate

Specifying a TLS client certificate and key

To ensure TLS connections to your origin come from Fastly and aren't random, anonymous requests, set your origin to verify the client using a client certificate. Simply paste the certificate and private key in PEM form into the appropriate text boxes on the TLS options page.

Then configure your backend to require client certificates and verify them against the CA cert they were signed with. Here are some ways of doing that:

Specifying acceptable TLS protocol versions

If your origin server is configured with support for modern TLS protocol versions, you can customize the TLS protocols Fastly will use to connect to it by setting a Minimum TLS Version and Maximum TLS Version under Advanced options. We recommend setting both to the most up-to-date TLS protocol, currently 1.3, if your origin can support it.

Use the openssl command to verify your origin supports a given TLS protocol version. For example:

openssl s_client -connect -tls1_3

Replace -tls1_3 with tls1_2, tls1_1 and tls1_0 to test other protocol versions. Fastly does not support SSLv2 or SSLv3.

Specifying acceptable TLS cipher suites

Fastly supports configuring the OpenSSL cipher suites used when connecting to your origin server. This allows you to turn specific cipher suites on or off based on security properties and origin server support. The Ciphersuites setting under Advanced options accepts an OpenSSL formatted cipher list. We recommend using the strongest cipher suite your origin will support as detailed by the Mozilla SSL Configuration Generator.

Use the openssl command to verify your origin supports a given cipher suite. For example:

openssl s_client -connect -tls1_2 -cipher ECDHE-RSA-AES128-GCM-SHA256

Replace -cipher ECDHE-RSA-AES128-GCM-SHA256 with the cipher suite to test.

What's next

Learn more about working with domains and working with health checks as you continue to refine versions of your service configurations.

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