Understanding Istio Traffic Routing: Gateways, VirtualServices, and DestinationRules

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Apr 18, 2025

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When working with Kubernetes, controlling traffic between services can get complicated. That’s where Istio comes in — it gives you fine-grained control over traffic inside and outside your cluster.

In this article, we’ll focus on three key Istio resources:

• Gateways — control inbound traffic from outside the cluster
• VirtualServices — define how traffic is routed inside the mesh
• DestinationRules — configure policies for traffic to specific service versions

Let’s break them down with a simple example and YAML snippets.

Scenario: You Have a Sample App with Two Versions

Imagine you have a service called my-app running two versions (v1 and v2). You want to:

• Allow external HTTP traffic to reach your app
• Route 80% of traffic to v1 and 20% to v2
• Enable connection policies like timeouts or TLS later on

We’ll do that using a Gateway, a VirtualService, and a DestinationRule.

Step 1: Gateway — Opening the…