1. Home
2. Guides
3. Getting started
4. Hosts

Ahost, also referred to as abackend ororigin, is a web server or cloud service that contains the content of your website or application. For example, a host could be a physical or virtual web server, an application running on a platform as a service, a serverless function running on a serverless platform, or even a static storage bucket.

Before Fastly can cache your content, you must add a host to yourFastly service configuration by specifying its hostname or IP address. When Fastly receives a request from a user, we fetch the objects from your host and return the response to the user.

Before you begin

Be sure you learn about theweb interface controls and how towork with services before you start working with your hosts.

Adding a host

To add a host to your Fastly service configuration, follow the steps below:

1. Log in to theFastly control panel.

2. From theHome page, select the appropriate service. You can use the search box to search by ID, name, or domain.

3. ClickEdit configuration and then select the option to clone the active version.

4. ClickOrigins.

5. ClickCreate a host.
6. Fill out theHosts 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. ClickAdd to add your host.

Editing a host

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

1. In theHosts area, click the pencil next to the Host you want to edit.

2. Fill out theEdit this host fields as follows:

   • In theName field, enter the name of your server (for example,My Origin Server). This name is displayed in the Fastly web interface.

   • In theAddress field, enter the IP address (or hostname) of your origin server.

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

   • In theIP version field, leave the checkbox selected to default to prefer IPv6 connections over IPv4 connections. If both IPv4 and IPv6 are available, IPv6 will be preferred, but not guaranteed. If the checkbox is deselected, IPv4 will be preferred, but not guaranteed.

     IMPORTANT: When working with Compute services, theIP version field is only supported with static backends, not dynamic backends.

3. Configure theTransport Layer Security (TLS) settings as follows:

   HINT: Running into errors when connecting to origins over TLS? Check out ourtroubleshooting guide.

   • From theEnable TLS? options, leave the default set toYes 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 selectNo if you do not want to use TLS.

   • From theVerify certificate? options, leave default set toYes if you want to verify the authenticity of the TLS certificate. SelectingNo means the certificate will not be verified.

     WARNING:

     Not verifying the certificate has serious security implications, including vulnerability to man-in-the-middle attacks. Consider uploading a CA certificate instead of disabling certificate validation.

   • In theCertificate 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.

   • (Optional) In theSNI hostname field, enter the hostname of a different certificate to be used for the request to origin if you are usingServer Name Indication (SNI) to put multiple certificates on your origin. Alternatively, select the checkbox to match the SNI hostname to the Certificate hostname. This information also gets sent to the server in the TLS handshake. See our guidance onunderstanding the difference between certificate hostname and SNI hostname values for additional details.

   • (Optional) In theTLS CA certificate field, provide a certificate in PEM format if you're using a certificate that is either self-signed or signed by a certification authority (CA) not commonly recognized by major browsers. The PEM format looks like this:

     

4. To apply advanced TLS options, clickAdvanced TLS options and decide which of the optional fields to specify, if any. For more information about these settings, seeAdvanced TLS options.

5. Configure the remainingCreate a host settings as follows:

   • (Optional) From theShielding menu, select a POP to enable the shielding feature. For more information, see our guide onshielding.

   • (Optional) From theHealth check menu, select a health check for this origin server. For more information, see our guide onworking with health checks.

   • (Optional) From theAuto load balance menu, selectYes to enable load balancing for this origin server. For more information, see our guide onload balancing.

   • If you enabled load balancing, enter a weight in theWeight field.

   • (Optional) In theOverride host field,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 theglobal override host configuration. To see example Host headers for third-party services, refer to our developer documentation onoverriding the Host header.

     HINT: To override the incoming Host header on your origin using your Fastly service, refer to theSpecifying the override host guide.

6. ClickAdvanced options and decide which of the optional fields to change, if any:

   • (Optional) In theMaximum connections field, 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.
   • (Optional) In theConnection timeout field, enter how long, in milliseconds, to wait for a connection timeout. The default is 1000 milliseconds.
   • (Optional) In theFirst byte timeout field, enter how long, in milliseconds, to wait for a first byte timeout. The default is 15000 milliseconds.
   • (Optional) In theBetween bytes timeout field, enter how long, in milliseconds, to wait between bytes. The default is 10000 milliseconds.

7. ClickUpdate. The new override host appears under theShow all details field of theOverride 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="example.com";
      .always_use_host_header=true;
       ...
   }

8. From theActivate menu, selectActivate on Production to deploy your configuration changes.

Advanced TLS options

If you enabled TLS for the connection between Fastly and your host, you can configure optional settings by clicking theAdvanced TLS options link.

Specifying acceptable TLS protocol versions

If your origin server supports modern TLS protocol versions, you can customize the TLS protocols Fastly will use to connect to it by setting aMinimum TLS Version andMaximum TLS Version. We recommend setting both to the most up-to-date TLS protocol, currently 1.3, if your origin supports it.

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

$ openssl s_client -connect origin.example.com:443 -tls1_3

Replace-tls1_3 withtls1_2,tls1_1 andtls1_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. TheCiphersuites setting accepts anOpenSSL formatted cipher list. We recommend using the strongest cipher suite your origin will support as detailed by theMozilla SSL Configuration Generator.

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

$ openssl s_client -connect origin.example.com:443 -tls1_2 -cipher ECDHE-RSA-AES128-GCM-SHA256

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

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 theTLS client certificate text box.

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:

• Apache
• NGINX
• IIS

Fastly also supports securing your connection to origin with mutual TLS (mTLS).

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 asssl_cert_hostname in VCL. This doesn't affect the SNI certification. You can set this value inCertificate hostname field.

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 asssl_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:

About thessl_hostname value (deprecated). Thessl_hostname value has been deprecated and replaced withssl_cert_hostname andssl_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), perRFC 6066.

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

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

What's next

Learn more aboutworking with domains andworking with health checks as you continue to refine versions of your service configurations.

Related content

• Integration with backend technologies
• TLS
• Backend API documentation