SNI for multiple SSL certificates in Nginx - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does SNI stand for and why is it important for multiple SSL certificates?

SNI stands for Server Name Indication. It allows a server to present multiple SSL certificates on the same IP address and port, enabling hosting of multiple secure websites without needing separate IPs.

intermediate

How does nginx use SNI to serve different SSL certificates?

nginx uses the server_name directive inside server blocks to match the requested hostname. It then selects the correct SSL certificate configured for that server block using SNI.

beginner

What is the minimum nginx configuration needed to enable SNI for two domains?

You need two server blocks each with its own server_name, ssl_certificate, and ssl_certificate_key directives. nginx automatically uses SNI to serve the right certificate based on the hostname.

intermediate

Can SNI work with clients that do not support it?

No, clients that do not support SNI will not be able to select the correct certificate and may see certificate warnings or connection failures.

beginner

Why is SNI preferred over using multiple IP addresses for SSL hosting?

SNI allows multiple SSL sites to share one IP address, saving IP resources and simplifying server management compared to assigning a unique IP for each SSL site.

What does SNI enable on a web server?

A Encrypting HTTP traffic without certificates

B Increasing server CPU speed

C Blocking unwanted IP addresses

D Serving multiple SSL certificates on one IP address

SNI allows a server to present different SSL certificates based on the hostname requested, all on the same IP address.

In nginx, which directive is used to specify the domain name for SNI?

A ssl_certificate

B listen

C server_name

D root

The server_name directive tells nginx which hostname this server block handles, enabling SNI to select the right certificate.

What happens if a client does not support SNI when connecting to an nginx server with multiple SSL certificates?

A The client may see a certificate warning or fail to connect

B The server automatically disables SSL

C The client receives all certificates

D The server redirects to HTTP

Without SNI support, the client cannot indicate which hostname it wants, so the server may send the wrong certificate causing warnings.

Which nginx directive specifies the SSL certificate file for a domain?

A ssl_certificate

B ssl_key

C ssl_certificate_key

D ssl_protocols

ssl_certificate points to the SSL certificate file for the domain in the server block.

Why is SNI useful for hosting multiple HTTPS sites on one server?

A It speeds up SSL handshake

B It allows sharing one IP address for many SSL sites

C It disables SSL for some sites

D It compresses SSL certificates

SNI lets multiple SSL certificates be used on a single IP, avoiding the need for multiple IP addresses.

Explain how nginx uses SNI to serve multiple SSL certificates on one IP address.

Think about how nginx matches the requested domain to the right certificate.

Describe the limitations of SNI and how it affects clients without SNI support.

Consider what happens if the client cannot tell the server which site it wants.