An SNI certificate is an extended server certificate that allows the same IP address and port number to provide multiple access domain names for external systems. Different security certificates can be used based on the domain names requested by clients to ensure HTTPS communication security.

When configuring SNI, you need to add a certificate associated with a domain name. The client submits the requested domain name information when initiating an SSL handshake request. After receiving the SSL request, the load balancer searches for the certificate based on the domain name. If the certificate is found, the load balancer will return it to the client. If the certificate is not found, the load balancer will return the default server certificate.

After SNI is configured, if you delete the SNI configuration on the CCE console or delete the target annotation from the YAML file, the configuration on the ELB will be retained.

Prerequisites

A Kubernetes cluster is available and the cluster version meets the following requirements:
- v1.23: v1.23.13-r0 or later
- v1.25: v1.25.8-r0 or later
- v1.27: v1.27.5-r0 or later
- v1.28: v1.28.3-r0 or later
- Other clusters of later versions

You have created one or more SNI certificates in ELB and specified a domain name in these certificates.
To create a cluster using commands, ensure kubectl is used. For details, see Accessing a Cluster Using kubectl.

Using the CCE Console

Log in to the CCE console and click the cluster name to access the cluster console.
In the navigation pane, choose Services & Ingresses. In the upper right corner, click Create Service.
Configure Service parameters. In this example, only mandatory parameters required for using SNI are listed. For details about how to configure other parameters, see Using the CCE Console.
- Service Name: Specify a Service name, which can be the same as the workload name.
- Service Type: Select LoadBalancer.
- Selector: Add a label and click Confirm. The Service will use this label to select pods. You can also click Reference Workload Label to use the label of an existing workload. In the dialog box that is displayed, select a workload and click OK.
- Load Balancer: Select a load balancer type and creation mode.
  - A load balancer can be dedicated or shared. To enable HTTP/HTTPS on the listener port of a dedicated load balancer, the type of the load balancer must be Application (HTTP/HTTPS) or Network (TCP/UDP) & Application (HTTP/HTTPS).
  - This section uses an existing load balancer as an example. For details about the parameters for automatically creating a load balancer, see Table 1.
- Port
  - Protocol: Select TCP. If you select UDP, HTTP and HTTPS will be unavailable.
  - Service Port: the port used by the Service. The port ranges from 1 to 65535.
  - Container Port: the port that the workload listens on. For example, Nginx uses port 80 by default.
  - Frontend Protocol: In this example, HTTPS must be enabled for the Service to use SNI. For a dedicated load balancer, to use HTTP/HTTPS, the type of the load balancer must be Application (HTTP/HTTPS).
- Listener
  - SSL Authentication: Select this option if Frontend Protocol is set to HTTPS. Dedicated load balancers are available in clusters of v1.23.14-r0, v1.25.9-r0, v1.27.6-r0, v1.28.4-r0, or later.
    - One-way authentication: Only the backend server is authenticated. If you also need to authenticate the identity of the client, select two-way authentication.
    - Two-way authentication: Both the clients and the load balancer authenticate each other. This ensures only authenticated clients can access the load balancer. No additional backend server configuration is required if you select this option.
  - CA Certificate: If SSL Authentication is set to Two-way authentication, add a CA certificate to authenticate the client. A CA certificate is issued by a Certificate Authority (CA) and is used to verify the issuer of the client's certificate. If HTTPS two-way authentication is enabled, HTTPS connections can be established only if the client provides a certificate issued by a specific CA.
  - Server Certificate: Select a server certificate as the default certificate.
  - SNI: Add an SNI certificate containing a domain name.
    If the server cannot find an SNI certificate matching the client-requested domain name, it will return the default server certificate.
  - Security Policy: If Frontend Protocol is set to HTTPS, you can select a security policy. This parameter is available only in clusters of v1.23.14-r0, v1.25.9-r0, v1.27.6-r0, v1.28.4-r0, or later.
  - Backend Protocol: If Frontend Protocol is set to HTTPS, HTTP or HTTPS can be used to access the backend server. The default value is HTTP. This parameter is available only in clusters of v1.23.14-r0, v1.25.9-r0, v1.27.6-r0, v1.28.4-r0, or later.
Click OK.

Using kubectl

This section uses an existing load balancer as an example. An example YAML file of a SNI-compliant Service is as follows:

apiVersion: v1
kind: Service
metadata:
  name: test
  labels:
    app: test
  namespace: default
  annotations:
    kubernetes.io/elb.class: performance        # Load balancer type
    kubernetes.io/elb.id: 65318265-4f01-4541-a654-fa74e439dfd3  # ID of an existing load balancer
    kubernetes.io/elb.protocol-port: https:80    # Port where SNI is to be enabled
    kubernetes.io/elb.cert-id: b64ab636f1614e1a960b5249c497a880    # HTTPS server certificate
    kubernetes.io/elb.tls-certificate-ids: 5196aa70b0f143189e4cb54991ba2286,8125d71fcc124aabbe007610cba42d60    # SNI certificate IDs
    kubernetes.io/elb.lb-algorithm: ROUND_ROBIN
spec:
  selector:
    app: test
  externalTrafficPolicy: Cluster
  ports:
    - name: cce-service-0
      targetPort: 80
      nodePort: 0
      port: 80
      protocol: TCP
  type: LoadBalancer
  loadBalancerIP: **.**.**.**       #  Private IP address of the load balancer

**Table 1** Key parameters
Parameter	Type	Description
kubernetes.io/elb.protocol-port	String	If a Service is HTTP/HTTPS-compliant, configure the protocol and port number in the format of "protocol:port". where, protocol: specifies the protocol used by the listener port. The value can be http or https. ports: Service ports specified by spec.ports[].port. For example, to use SNI, the Service protocol must be https and the Service port must be 80. Therefore, the parameter value is https:80.
kubernetes.io/elb.cert-id	String	ID of an ELB certificate, which is used as the HTTPS server certificate. How to obtain: Log in to the ELB console and choose Certificates. In the certificate list, copy the ID under the target certificate name.
kubernetes.io/elb.tls-certificate-ids	String	In ELB, the IDs of SNI certificates that must contain a domain name are separated by commas (,). If the server cannot find an SNI certificate matching the client-requested domain name, it will return the default server certificate. How to obtain: Log in to the ELB console and choose Certificates. In the certificate list, copy the ID under the target certificate name.
kubernetes.io/elb.client-ca-cert-id	String	Required only for mutual authentication. The ELB certificate ID serves as the CA certificate. How to obtain: Log in to the ELB console and choose Certificates. In the certificate list, copy the ID under the target certificate name. Dedicated load balancers are available in clusters of v1.23.14-r0, v1.25.9-r0, v1.27.6-r0, v1.28.4-r0, or later.

Configuring SNI for a LoadBalancer Service

Prerequisites

Using the CCE Console

Using kubectl