Traefik Traefik not respecting SNI rules

What is Traefik Traefik not respecting SNI rules

Understanding Traefik and Its Purpose

Traefik is a modern HTTP reverse proxy and load balancer that makes deploying microservices easy. It is designed to integrate with your existing infrastructure components and provides dynamic configuration capabilities. Traefik supports multiple backends, including Docker, Kubernetes, and more, making it a versatile tool for managing traffic in a microservices architecture.

Identifying the Symptom: Traefik Not Respecting SNI Rules

When using Traefik, you might encounter a situation where it does not respect Server Name Indication (SNI) rules. This issue manifests as Traefik not routing traffic based on the SNI, leading to requests being directed to the wrong backend service or resulting in SSL handshake failures.

Exploring the Issue: SNI-Based Routing

SNI is an extension to the TLS protocol that allows a client to specify the hostname it is trying to connect to at the start of the handshake process. Traefik uses SNI to route traffic to the appropriate backend based on the hostname. If SNI rules are not respected, it could be due to misconfiguration or an oversight in the setup.

Common Causes of SNI Issues

Incorrect or missing SNI configuration in Traefik's dynamic configuration. SSL certificates not properly associated with the intended hostnames. Misconfigured entry points or routers in Traefik.

Steps to Fix the SNI Issue in Traefik

To resolve the issue of Traefik not respecting SNI rules, follow these steps:

Step 1: Verify SNI Rule Configuration

Check your Traefik configuration files to ensure that SNI rules are correctly defined. This includes verifying the tls section in your routers and ensuring that the domains and certificates are correctly specified.

http: routers: my-router: rule: "Host(`example.com`) tls: domains: - main: "example.com" sans: - "www.example.com"

Step 2: Check SSL Certificate Associations

Ensure that the SSL certificates are correctly associated with the intended hostnames. Use the Traefik documentation to verify the correct setup of certificates.

Step 3: Review Entry Points and Routers

Make sure that your entry points and routers are configured to handle TLS traffic. Check that the entry points are listening on the correct ports and that routers are correctly linked to these entry points.

entryPoints: websecure: address: ":443"

Conclusion

By following these steps, you should be able to resolve issues related to Traefik not respecting SNI rules. Proper configuration of SNI rules, SSL certificates, and entry points is crucial for ensuring that Traefik routes traffic correctly based on the hostname. For more detailed guidance, refer to the Traefik Routing Documentation.