consul/website/content/docs/connect/gateways/mesh-gateway/peering-via-mesh-gateways.mdx

---
layout: docs
page_title: Enabling Peering Control Plane Traffic
description: >-
  Mesh gateways are specialized proxies that route data between services that cannot communicate directly. Learn how to enable traffic across clusters in different datacenters or admin partitions that have an established peering connection.
---

# Enabling Peering Control Plane Traffic

In addition to [service-to-service traffic routing](/consul/docs/connect/gateways/mesh-gateway/service-to-service-traffic-peers),
we recommend routing control plane traffic between cluster peers through mesh gateways
to simplfy networking requirements.

Control plane traffic between cluster peers includes
the initial secret handshake and the bi-directional stream replicating peering data.
This data is not decrypted by the mesh gateway(s).
Instead, it is transmitted end-to-end using the accepting cluster’s auto-generated TLS certificate on the gRPC TLS port.

<Tabs>
<Tab heading="With mesh gateways (recommended)">

[![Cluster peering with mesh gateways](/img/consul-connect/mesh-gateway/cluster-peering-connectivity-with-mesh-gateways.png)](/img/consul-connect/mesh-gateway/cluster-peering-connectivity-with-mesh-gateways.png)

</Tab>

<Tab heading="Without mesh gateways">

[![Cluster peering without mesh gateways](/img/consul-connect/mesh-gateway/cluster-peering-connectivity-without-mesh-gateways.png)](/img/consul-connect/mesh-gateway/cluster-peering-connectivity-without-mesh-gateways.png)

</Tab>
</Tabs>

## Prerequisites

To configure mesh gateways for cluster peering control plane traffic, make sure your Consul environment meets the following requirements:

- Consul version 1.14.0 or newer.
- A local Consul agent in both clusters is required to manage mesh gateway configuration.
- Use [Envoy proxies](/consul/docs/connect/proxies/envoy). Envoy is the only proxy with mesh gateway capabilities in Consul.

## Configuration

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

### Gateway registration

Register a mesh gateway in each of cluster that will be peered.

- Specify `mesh-gateway` in the `kind` field to register the gateway with Consul.
- Define the `Proxy.Config` settings using opaque parameters compatible with your proxy. For Envoy, refer to the [Gateway Options](/consul/docs/connect/proxies/envoy#gateway-options) and [Escape-hatch Overrides](/consul/docs/connect/proxies/envoy#escape-hatch-overrides) documentation for additional configuration information.
- Apply a [Mesh config entry](/consul/docs/connect/config-entries/mesh#peer-through-mesh-gateways) with `PeerThroughMeshGateways = true`. See [modes](#modes) for a discussion of when to apply this.

Alternatively, you can also use the CLI to spin up and register a gateway in Consul. For additional information, refer to the [`consul connect envoy` command](/consul/commands/connect/envoy#mesh-gateways).

For Consul Enterprise clusters, mesh gateways must be registered in the "default" partition because this is implicitly where Consul servers are assigned.

### ACL configuration

<Tabs>
<Tab heading="Consul OSS">

In addition to the [ACL Configuration](/consul/docs/connect/gateways/mesh-gateway/service-to-service-traffic-peers#acl-configuration) necessary for service-to-service traffic, mesh gateways that route peering control plane traffic must be granted `peering:read` access to all peerings. 
This access allows the mesh gateway to list all peerings in a Consul cluster and generate unique routing per peered datacenter.

<CodeTabs heading="Example ACL rules for Mesh Gateway Peering Control Plane Traffic in Consul OSS">

```hcl
peering = "read"
```

```json
{
  "peering": "read"
}
```

</CodeTabs>

</Tab>

<Tab heading="Consul Enterprise">

In addition to the [ACL Configuration](/consul/docs/connect/gateways/mesh-gateway/service-to-service-traffic-peers#acl-configuration) necessary for service-to-service traffic, mesh gateways that route peering control plane traffic must be granted `peering:read` access to all peerings in all partitions. 
This access allows the mesh gateway to list all peerings in a Consul cluster and generate unique routing per peered partition.

<CodeTabs heading="Example ACL rules for Mesh Gateway Peering Control Plane Traffic in Consul Enterprise">

```hcl
partition_prefix "" {
	peering = "read"
}
```

```json
{
  "partition_prefix": {
    "": {
	  "peering": "read"
	}
  }
}
```

</CodeTabs>

</Tab>
</Tabs>

### Modes

Connect proxy configuration [Modes](/consul/docs/connect/gateways/mesh-gateway#connect-proxy-configuration#modes) are not applicable to peering control plane traffic. 
The flow of control plane traffic through the gateway is implied by the presence of a [Mesh config entry](/consul/docs/connect/config-entries/mesh#peer-through-mesh-gateways) with `PeerThroughMeshGateways = true`.

<CodeTabs heading="Example: Enabling Peering Control Plane Traffic for Mesh Gateways">

```hcl
Kind = "mesh"
Peering {
   PeerThroughMeshGateways = true
}
```

```yaml
Kind: mesh
Peeering:
  PeerThroughMeshGateways: true
```
</CodeTabs>

By setting this mesh config on a cluster before [creating a peering token](/consul/docs/connect/cluster-peering/usage/establish-cluster-peering#create-a-peering-token), inbound control plane traffic will be sent through the mesh gateway registered this cluster, also known the accepting cluster. 
As mesh gateway instances are registered at the accepting cluster, their addresses will be exposed to the dialing cluster over the bi-directional peering stream.

Setting this mesh config on a cluster before [establishing a connection](/consul/docs/connect/cluster-peering/usage/establish-cluster-peering#establish-a-connection-between-clusters) will cause the outbound control plane traffic to flow through the mesh gateway.

To route all peering control plane traffic though mesh gateways, both the accepting and dialing cluster must have the mesh config entry applied.