# gRPC routing !!! info "Experimental Channel" The `GRPCRoute` resource described below is currently only included in the "Experimental" channel of Gateway API. For more information on release channels, refer to our [versioning guide](/concepts/versioning). The [GRPCRoute resource](/api-types/grpcroute) allows you to match on gRPC traffic and direct it to Kubernetes backends. This guide shows how the GRPCRoute matches traffic on host, header, and service, and method fields and forwards it to different Kubernetes Services. The following diagram describes a required traffic flow across three different Services: - Traffic to `foo.example.com` for the `com.Example.Login` method is forwarded to `foo-svc` - Traffic to `bar.example.com` with an `env: canary` header is forwarded to `bar-svc-canary` for all services and methods - Traffic to `bar.example.com` without the header is forwarded to `bar-svc` for all services and methods ![gRPC Routing](/images/grpc-routing.png) The dotted lines show the `Gateway` resources deployed to configure this routing behavior. There are two `GRPCRoute` resources that create routing rules on the same `prod` Gateway. This illustrates how more than one Route can bind to a Gateway which allows Routes to merge on a `Gateway` as long as they don't conflict. `GRPCRoute` follows the same Route merging semantics. For more information on that, refer to the [documentation](/api-types/httproute#merging). In order to receive traffic from a [Gateway][gateway], a `GRPCRoute` resource must be configured with `ParentRefs` which reference the parent gateway(s) that it should be attached to. The following example shows how the combination of `Gateway` and `GRPCRoute` would be configured to serve gRPC traffic: ```yaml {% include 'standard/grpc-routing/gateway.yaml' %} ``` A `GRPCRoute` can match against a [single set of hostnames][spec]. These hostnames are matched before any other matching within the GRPCRoute takes place. Since `foo.example.com` and `bar.example.com` are separate hosts with different routing requirements, each is deployed as its own GRPCRoute - `foo-route` and `bar-route`. The following `foo-route` will match any traffic for `foo.example.com` and apply its routing rules to forward the traffic to the correct backend. Since there is only one match specified, only requests for the `com.example.User.Login` method to `foo.example.com` will be forwarded. RPCs of any other method` will not be matched by this Route. ```yaml {% include 'standard/grpc-routing/foo-grpcroute.yaml' %} ``` Similarly, the `bar-route` GRPCRoute matches RPCs for `bar.example.com`. All traffic for this hostname will be evaluated against the routing rules. The most specific match will take precedence which means that any traffic with the `env: canary` header will be forwarded to `bar-svc-canary` and if the header is missing or does not have the value `canary` then it will be forwarded to `bar-svc`. ```yaml {% include 'standard/grpc-routing/bar-grpcroute.yaml' %} ``` [gRPC Reflection](https://github.com/grpc/grpc/blob/v1.49.1/doc/server-reflection.md) is required to use interactive clients such as [`grpcurl`](https://github.com/fullstorydev/grpcurl) without having a local copy of the target service's protocol buffers present on your local filesysem. To enable this, first ensure that you have a gRPC reflection server listening on your application pods, then add the reflection method to your `GRPCRoute`. This is likely to be useful in development and staging environments, but this should be enabled in production environments only after the security implications have been considered. ```yaml {% include 'standard/grpc-routing/reflection-grpcroute.yaml' %} ``` [gateway]: /reference/spec/#gateway.networking.k8s.io/v1.Gateway [spec]: /reference/spec/#gateway.networking.k8s.io%2fv1alpha2.GRPCRouteSpec [svc]:https://kubernetes.io/docs/concepts/services-networking/service/