---
layout: docs
page_title: Mesh Gateways
description: >-
  Mesh gateways are specialized proxies that route data between services that cannot communicate directly. Learn how mesh gateways are used in different Consul configurations.
---

# Mesh Gateways

Mesh gateways enable service mesh traffic to be routed between different Consul datacenters.
Datacenters can reside in different clouds or runtime environments where general interconnectivity between all services in all datacenters isn't feasible.

## Prerequisites

Mesh gateways can be used with any of the following Consul configrations for managing separate datacenters or partitions.

1. WAN Federation
  * [Mesh gateways can be used to route service-to-service traffic between datacenters](/docs/connect/gateways/mesh-gateway/service-to-service-traffic-wan-datacenters)
  * [Mesh gateways can be used to route all WAN traffic, including from Consul servers](/docs/connect/gateways/mesh-gateway/wan-federation-via-mesh-gateways)
2. Cluster Peering
  * [Mesh gateways can be used to route service-to-service traffic between datacenters](/docs/connect/gateways/mesh-gateway/service-to-service-traffic-peers)
  * [Mesh gateways can be used to route control-plane traffic from Consul servers](/docs/connect/gateways/mesh-gateway/peering-via-mesh-gateways)
3. Admin Partitions
  * [Mesh gateways can be used to route service-to-service traffic between admin partitions in the same Consul datacenter](/docs/connect/gateways/mesh-gateway/service-to-service-traffic-partitions)

### Consul

Review the [specific guide](#prerequisites) for your use case to determined the required version of Consul.

### Network

* General network connectivity to all services within its local Consul datacenter.
* General network connectivity to all mesh gateways within remote Consul datacenters.

### Proxy

Envoy is the only proxy with mesh gateway capabilities in Consul.

Mesh gateway proxies receive their configuration through Consul, which automatically generates it based on the proxy's registration.
Consul can only translate mesh gateway registration information into Envoy configuration.

Sidecar proxies that send traffic to an upstream service through a gateway need to know the location of that gateway. They discover the gateway based on their sidecar proxy registrations. Consul can only translate the gateway registration information into Envoy configuration.

Sidecar proxies that do not send upstream traffic through a gateway are not affected when you deploy gateways. If you are using Consul's built-in proxy as a Connect sidecar it will continue to work for intra-datacenter traffic and will receive incoming traffic even if that traffic has passed through a gateway.

## Configuration

Configure the following settings to register the mesh gateway as a service in Consul.

* Specify `mesh-gateway` in the `kind` field to register the gateway with Consul.
* Configure the `proxy.upstreams` parameters to route traffic to the correct service, namespace, and datacenter. Refer to the [`upstreams` documentation](/docs/connect/registration/service-registration#upstream-configuration-reference) for details. The service `proxy.upstreams.destination_name` is always required. The `proxy.upstreams.datacenter` must be configured to enable cross-datacenter traffic. The `proxy.upstreams.destination_namespace` configuration is only necessary if the destination service is in a different namespace.
* Define the `Proxy.Config` settings using opaque parameters compatible with your proxy (i.e., Envoy). For Envoy, refer to the [Gateway Options](/docs/connect/proxies/envoy#gateway-options) and [Escape-hatch Overrides](/docs/connect/proxies/envoy#escape-hatch-overrides) documentation for additional configuration information.
* If ACLs are enabled, a token granting `service:write` for the gateway's service name and `service:read` for all services in the datacenter or partition must be added to the gateway's service definition. These permissions authorize the token to route communications for other Consul service mesh services, but does not allow decrypting any of their communications.

### Modes

Each upstream associated with a service mesh proxy can be configured so that it is routed through a mesh gateway.
Depending on your network, the proxy's connection to the gateway can operate in one of the following modes:

* `none` - No gateway is used and a service mesh connect proxy makes its outbound connections directly
  to the destination services. This is the default for WAN federation. This setting is invalid for peered clusters
  and will be treated as remote instead. 

* `local` - The service mesh connect proxy makes an outbound connection to a gateway running in the
  same datacenter. That gateway is responsible for ensuring that the data is forwarded to gateways in the destination datacenter.

* `remote` - The service mesh proxy makes an outbound connection to a gateway running in the destination datacenter.
  The gateway forwards the data to the final destination service. This is the default for peered clusters.

### Connect Proxy Configuration

Set the proxy to the preferred [mode](#modes) to configure the service mesh proxy. You can specify the mode globally or within child configurations to control proxy behaviors at a lower level. Consul recognizes the following order of precedence if the gateway mode is configured in multiple locations the order of precedence:

1. Upstream definition (highest priority)
2. Service instance definition
3. Centralized `service-defaults` configuration entry
4. Centralized `proxy-defaults` configuration entry

## Example Configurations

Use the following example configurations to help you understand some of the common scenarios.

### Enabling Gateways Globally

The following `proxy-defaults` configuration will enable gateways for all Connect services in the `local` mode.

<CodeTabs heading="Example: Enabling gateways globally.">

```hcl
Kind = "proxy-defaults"
Name = "global"
MeshGateway {
   Mode = "local"
}
```

```yaml
Kind: proxy-defaults
MeshGateway:
- Mode: local
Name: global
```
</CodeTabs>

### Enabling Gateways Per Service

The following `service-defaults` configuration will enable gateways for all Connect services with the name `web`.

<CodeTabs heading="Example: Enabling gateways per service.">

```hcl
Kind = "service-defaults"
Name = "web"
MeshGateway {
   Mode = "local"
}
```

```yaml
Kind: service-defaults
MeshGateway:
- Mode: local
Name: web
```

</CodeTabs>

### Enabling Gateways for a Service Instance

The following [Proxy Service Registration](/docs/connect/registration/service-registration)
definition will enable gateways for the service instance in the `remote` mode.

<CodeTabs heading="Example: Enabling gateways for a service instance.">

```hcl
service {
   name = "web-sidecar-proxy"
   kind = "connect-proxy"
   port = 8181
   proxy {
      destination_service_name = "web"
      mesh_gateway {
         mode = "remote"
      }
      upstreams = [
         {
            destination_name = "api"
            datacenter = "secondary"
            local_bind_port = 10000
         }
      ]
   }
}

# Or alternatively inline with the service definition:

service {
  name = "web"
  port = 8181
  connect {
    sidecar_service {
      proxy {
        mesh_gateway {
         mode = "remote"
        }
        upstreams = [
          {
            destination_name = "api"
            datacenter = "secondary"
            local_bind_port = 10000
          }
        ]
      }
    }
  }
}
```

```yaml
service:
- kind: connect-proxy
  name: web-sidecar-proxy
  port: 8181
  proxy:
  - destination_service_name: web
    mesh_gateway:
    - mode: remote
    upstreams:
    - datacenter: secondary
      destination_name: api
      local_bind_port: 100
```

</CodeTabs>

### Enabling Gateways for a Proxy Upstream

The following service definition will enable gateways in the `local` mode for one upstream, the `remote` mode for a second upstream and will disable gateways for a third upstream.

<CodeTabs heading="Example: Enabling gateways for a proxy upstream.">

```hcl
service {
   name = "web-sidecar-proxy"
   kind = "connect-proxy"
   port = 8181
   proxy {
      destination_service_name = "web"
      upstreams = [
         {
            destination_name = "api"
            local_bind_port = 10000
            mesh_gateway {
               mode = "remote"
            }
         },
         {
            destination_name = "db"
            local_bind_port = 10001
            mesh_gateway {
               mode = "local"
            }
         },
         {
            destination_name = "logging"
            local_bind_port = 10002
            mesh_gateway {
               mode = "none"
            }
         },
      ]
   }
}
```
```yaml
service:
- kind: connect-proxy
  name: web-sidecar-proxy
  port: 8181
  proxy:
  - destination_service_name: web
    upstreams:
    - destination_name: api
      local_bind_port: 10000
      mesh_gateway:
      - mode: remote
    - destination_name: db
      local_bind_port: 10001
      mesh_gateway:
      - mode: local
    - destination_name: logging
      local_bind_port: 10002
      mesh_gateway:
      - mode: none
  ```
  </CodeTabs>
