---
layout: docs
page_title: Gateway Resource Configuration
description: >-
  Learn how to configure the `Gateway` resource to define how the Consul API Gateway handles incoming service mesh traffic with this configuration model and reference specifications.
---

# Gateway Resource Configuration

This topic provides full details about the `Gateway` resource.

## Introduction

A `Gateway` is an instance of network infrastructure that determines how service traffic should be handled. A `Gateway` contains one or more [`listeners`](#listeners) that bind to a set of IP addresses. An `HTTPRoute` or `TCPRoute` can then attach to a gateway listener to direct traffic from the gateway to a service.

Gateway instances derive their configurations from the [`GatewayClass`](/consul/docs/connect/gateways/api-gateway/configuration/gatewayclass) resource, which acts as a template for individual `Gateway` deployments. Refer to [GatewayClass](/consul/docs/connect/gateways/api-gateway/configuration/gatewayclass) for additional information.

Specify the following parameters to declare a `Gateway`:

|  Parameter  |                                                                         Description                                                                          | Required |
| :-----------  |:---------------------------------------------------------------------------------------------------------------------------------------------------------- |:-------- |
| `kind`        | Specifies the type of configuration object. The value should always be `Gateway`.                                                                             | Required |
| `description` | Human-readable string that describes the purpose of the `Gateway`.                                                                                           | Optional |
| `version `    | Specifies the Kubernetes API version. The value should always be `gateway.networking.k8s.io/v1alpha2`                                                        | Required |
| `scope`       | Specifies the effective scope of the Gateway. The value should always be `namespaced`.                                                                       | Required |
| `fields`      | Specifies the configurations for the Gateway. The fields are listed in the [configuration model](#configuration-model). Details for each field are described in the [specification](#specification). | Required |


## Configuration model

The following outline shows how to format the configurations in the `Gateway` object. Click on a property name to view details about the configuration.

* [`gatewayClassName`](#gatewayclassname): string | required
* [`listeners`](#listeners): array of objects | required
  * [`allowedRoutes`](#listeners-allowedroutes): object | required
    * [`namespaces`](#listeners-allowedroutes-namespaces): object | required
      * [`from`](#listeners-namespaces-from): string | required
      * [`selector`](#listeners-allowedroutes-namespaces-selector): object | required if `from` is configured to `selector`
        * [`matchExpressions`](#listeners-allowedroutes-namespaces-selector-matchexpressions): array of objects | required if `matchLabels` is not configured
          * [`key`](#listeners-allowedroutes-namespaces-selector-matchexpressions): string | required if `matchExpressions` is declared
          * [`operator`](#listeners-allowedroutes-namespaces-selector-matchexpressions): string | required if `matchExpressions` is declared
          * [`values`](#listeners-allowedroutes-namespaces-selector-matchexpressions): array of strings | required if `matchExpressions` is declared
        * [`matchLabels`](#listeners-allowedroutes-namespaces-selector-matchlabels): map of strings | required if `matchExpressions` is not configured
  * [`hostname`](#listeners-hostname): string | required
  * [`name`](#listeners-name): string | required
  * [`port`](#listeners-port): integer | required
  * [`protocol`](#listeners-protocol): string | required
  * [`tls`](#listeners-tls): object | required if `protocol` is set to `HTTPS`
      * [`certificateRefs`](#listeners-tls): array or objects | required if `tls` is declared
        * [`name`](#listeners-tls): string | required if `certificateRefs` is declared
        * [`namespace`](#listeners-tls): string | required if `certificateRefs` is declared
      * [`mode`](#listeners-tls): string | required if `certificateRefs` is declared
      * [`options`](#listeners-tls): map of strings | optional

## Specification

This topic provides details about the configuration parameters.

### gatewayClassName
Specifies the name of the [`GatewayClass`](/consul/docs/connect/gateways/api-gateway/configuration/gatewayclass) resource used for the `Gateway` instance. Unless you are using a custom [GatewayClass](/consul/docs/connect/gateways/api-gateway/configuration/gatewayclass), this value should be set to `consul`.
* Type: string
* Required: required

### listeners
Specifies the `listeners` associated with the `Gateway`. At least one `listener` must be specified. Each `listener` within a `Gateway` must have a unique combination of `hostname`, `port`, and `protocol`.
* Type: array of objects
* Required: required

### listeners.allowedRoutes
Specifies a `namespace` object that defines the types of routes that may be attached to a listener.
* Type: object
* Required: required

### listeners.allowedRoutes.namespaces
Determines which routes are allowed to attach to the `listener`. Only routes in the same namespace as the `Gateway` may be attached by default.
* Type: string
* Required: optional
* Default:  Same namespace as the parent Gateway

### listeners.allowedRoutes.namespaces.from
Determines which namespaces are allowed to attach a route to the `Gateway`. You can specify one of the following strings:

* `All`: Routes in all namespaces may be attached to the `Gateway`.
* `Same` (default): Only routes in the same namespace as the `Gateway` may be attached.
* `Selector`: Only routes in namespaces that match the [`selector`](#listeners-allowedroutes-namespaces-selector) may be attached.

This parameter is required.

### listeners.allowedRoutes.namespaces.selector
Specifies a method for selecting routes that are allowed to attach to the listener. The `Gateway` checks for namespaces in the network that match either a regular expression or a label. Routes from the matching namespace are allowed to attach to the listener.

You can configure one of the following objects:

* [`matchExpressions`](#listeners-allowedroutes-namespaces-selector-matchexpressions)
* [`matchLabels`](#listeners-allowedroutes-namespaces-selector-matchlabels)

This field is required when [`from`](#listeners-allowedroutes-namespaces-from) is configured to `Selector`.

### listeners.allowedRoutes.namespaces.selector.matchExpressions
Specifies an array of requirements for matching namespaces. If a match is found, then routes from the matching namespace(s) are allowed to attach to the `Gateway`. The following table describes members of the `matchExpressions` array:

| Requirement | Description | Type | Required |
|--- |--- |--- |--- |
|`key` | Specifies the label that the `key` applies to. | string | required when `matchExpressions` is declared |
|`operator` | Specifies the key's relation to a set of values. You can use the following keywords: <ul><li>`In`: Only routes in namespaces that contain the strings in the `values` field can attach to the `Gateway`. </li><li>`NotIn`: Routes in namespaces that do not contain the strings in the `values` field can attach to the `Gateway`. </li><li>`Exists`: Routes in namespaces that contain the `key` value are allowed to attach to the `Gateway`.</li><li>`DoesNotExist`: Routes in namespaces that do not contain the `key` value are allowed to attach to the `Gateway`.</li></ul> | string | required when `matchExpressions` is declared |
|`values` | Specifies an array of string values. If `operator` is configured to `In` or `NotIn`, then the `values` array must contain values. If `operator` is configured to `Exists` or `DoesNotExist`, then the `values` array must be empty. | array of strings | required when `matchExpressions` is declared |

In the following example, routes in namespaces that contain `foo` and `bar` are allowed to attach routes to the `Gateway`.
```yaml
namespaceSelector:
  matchExpressions:
  - key: kubernetes.io/metadata.name
    operator: In
    values:
    - foo
    - bar
```

Refer to [Labels and Selectors](https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/#resources-that-support-set-based-requirements) in the Kubernetes documentation for additional information about `matchExpressions`.

### listeners.allowedRoutes.namespaces.selector.matchLabels
Specifies an array of labels and label values. If a match is found, then routes with the matching label(s) are allowed to attach to the `Gateway`. This selector can contain any arbitrary key/value pair.

In the following example, routes in namespaces that have a `bar` label are allowed to attach to the `Gateway`.

```yaml
namespaceSelector:
    matchLabels:
      foo: bar
```

Refer to [Labels and Selectors](https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/) in the Kubernetes documentation for additional information about labels.

### listeners.hostname
Specifies the `listener`'s hostname.
* Type: string
* Required: required

### listeners.name
Specifies the `listener`'s name.
* Type: string
* Required: required

### listeners.port
Specifies the port number that the `listener` attaches to.
* Type: integer
* Required: required

### listeners.protocol
Specifies the protocol the `listener` communicates on.
* Type: string
* Required: required

Allowed values are `TCP`, `HTTP`, or `HTTPS`

### listeners.tls
Specifies the `tls` configurations for the `Gateway`. The `tls` object is required if `protocol` is set to `HTTPS`. The object contains the following fields:

| Parameter | Description | Type | Required |
| ---       | ---         | ---  | ---      |
| `certificateRefs` | <div style={{width:480}}>Specifies Kubernetes `name` and `namespace` objects that contains TLS certificates and private keys. <br/>The certificates establish a TLS handshake for requests that match the `hostname` of the associated `listener`. Each reference must be a Kubernetes Secret. If you are using a Secret in a namespace other than the `Gateway`'s, each reference must also have a corresponding [`ReferenceGrant`](https://gateway-api.sigs.k8s.io/v1alpha2/references/spec/#gateway.networking.k8s.io/v1alpha2.ReferenceGrant).</div>  | Object or array | Required if `tls` is set |
| `mode` | Specifies the TLS Mode. Should always be set to `Terminate` for `HTTPRoutes` | string | Required if `certificateRefs` is set |
| `options` | Specifies additional Consul API Gateway options. | Map of strings | optional |

The following keys for `options` are available
* `api-gateway.consul.hashicorp.com/tls_min_version`
* `api-gateway.consul.hashicorp.com/tls_max_version`
* `api-gateway.consul.hashicorp.com/tls_cipher_suites`

In the following example, `tls` settings are configured to use a secret named `consul-server-cert` in the same namespace as the `Gateway` and the minimum tls version is set to `TLSv1_2`.

```yaml

tls:
  certificateRefs:
  - name: consul-server-cert
    group: ""
    kind: Secret
  mode: Terminate
  options:
    api-gateway.consul.hashicorp.com/tls_min_version: "TLSv1_2"

```

#### Example cross-namespace certificateRef

The following example creates a `Gateway` named `example-gateway` in namespace `gateway-namespace` (lines 2-4). The gateway has a `certificateRef` in namespace `secret-namespace` (lines 16-18). The reference is allowed because the `ReferenceGrant` configuration, named `reference-grant` in namespace `secret-namespace` (lines 24-27), allows `Gateways` in `gateway-namespace` to reference `Secrets` in `secret-namespace` (lines 31-35).

<CodeBlockConfig filename="gateway_with_referencegrant.yaml" lineNumbers highlight="2-4,16-18,24-27,31-35">

  ```yaml
  apiVersion: gateway.networking.k8s.io/v1beta1
  kind: Gateway
  metadata:
    name: example-gateway
    namespace: gateway-namespace
  spec:
    gatewayClassName: consul
    listeners:
    - protocol: HTTPS
      port: 443
      name: https
      allowedRoutes:
        namespaces:
          from: Same
      tls:
        certificateRefs:
          - name: cert
            namespace: secret-namespace
            group: ""
            kind: Secret
  ---

  apiVersion: gateway.networking.k8s.io/v1alpha2
  kind: ReferenceGrant
  metadata:
    name: reference-grant
    namespace: secret-namespace
  spec:
    from:
    - group: gateway.networking.k8s.io
      kind: Gateway
      namespace: gateway-namespace
    to:
    - group: ""
      kind: Secret
      name: cert
  ```

</CodeBlockConfig>
