open-consul/website/content/docs/connect/transparent-proxy.mdx

---
layout: docs
page_title: Connect - Transparent Proxy
sidebar_title: Transparent Proxy <sup>Beta</sup>
description: |-
  Transparent proxy is used to direct inbound and outbound traffic to services via the Envoy proxy and configure
  upstreams via intentions.
---

# Transparent Proxy <sup>Beta</sup>

Transparent proxy allows users to reach other services in the service mesh while ensuring that inbound and outbound
traffic for services in the mesh are directed through the sidecar proxy. This makes it more likely that traffic is secure
and only reaches intended destinations since the proxy can enforce security and policy like TLS and Service Intentions.

Previously, service mesh users would need to explicitly define upstreams for a service as a local listener on the sidecar
proxy, and dial the local listener to reach the appropriate upstream. Users would also have to set intentions to allow
specific services to talk to one another. Transparent proxying reduces this duplication, by determining upstreams
implicitly from Service Intentions. Explicit upstreams are still supported in the [proxy service
registration](/docs/connect/registration/service-registration) on VMs and via the
[annotation](/docs/k8s/connect#consul-hashicorp-com-connect-service-upstreams) in Kubernetes.

To support transparent proxying, Consul's CLI now has a command
[`consul connect redirect-traffic`](/commands/connect/redirect-traffic) to redirect traffic through an inbound and
outbound listener on the sidecar. Consul also watches Service Intentions and configures the Envoy proxy with the appropriate
upstream IPs. If the default ACL policy is "allow", then Service Intentions are not required. In Consul on Kubernetes,
the traffic redirection command is automatically set up via an init container.

## Prerequisites

### Kubernetes

* To use transparent proxy on Kubernetes, Consul-helm >= `0.32.0` and Consul-k8s >= `0.26.0` are required in addition to
the Consul >= `1.10.0`.
* If the default policy for ACLs is "deny", then Service Intentions should be set up to allow intended services to connect to each other.
Otherwise, all Connect services can talk to all other services.

The Kubernetes integration takes care of registering Kubernetes services with Consul, injecting a sidecar proxy, and
enabling traffic redirection.


## Configuration

Transparent proxy can be enabled in Kubernetes on the whole cluster via the Helm value:

```yaml
connectInject:
  transparentProxy:
    defaultEnabled: true
```

It can also be enabled on a per service basis via the annotation `consul.hashicorp.com/transparent-proxy=true` on the
Pod for each service:

```yaml
apiVersion: v1
kind: Service
metadata:
  name: static-server
spec:
  selector:
    app: static-server
  ports:
    - protocol: TCP
      port: 80
      targetPort: 8080
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: static-server
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: static-server
spec:
  replicas: 1
  selector:
    matchLabels:
      app: static-server
  template:
    metadata:
      name: static-server
      labels:
        app: static-server
      annotations:
        'consul.hashicorp.com/connect-inject': 'true'
        'consul.hashicorp.com/transparent-proxy': 'true'
    spec:
      containers:
        - name: static-server
          image: hashicorp/http-echo:latest
          args:
            - -text="hello world"
            - -listen=:8080
          ports:
            - containerPort: 8080
              name: http
      serviceAccountName: static-server
```

## Known Beta Limitations

* There is no first class support for transparent proxying on VMs. 
* Traffic can only be transparently proxied when the address dialed corresponds to the address of a service in the 
transparent proxy's datacenter. Cross-datacenter transparent proxying is only possible using service-resolver
configuration entries that resolve to remote datacenters.
* When dialing headless services the request will be proxied using a plain TCP proxy with a 5s connection timeout.
Currently the upstream's protocol and connection timeout are not considered.

## Using Transparent Proxy

In Kubernetes, services can reach other services via their
[KubeDNS](https://kubernetes.io/docs/concepts/services-networking/dns-pod-service/) address or via Pod IPs, and that
traffic will be transparently sent through the proxy. Connect services in Kubernetes are required to have a Kubernetes
service selecting the Pods.

~> Note: In order to use KubeDNS, the Kubernetes service name will need to match the Consul service name. This will be the
case by default, unless the service Pods have the annotation `consul.hashicorp.com/connect-service` overriding the
Consul service name.

Transparent proxy is enabled by default in Consul-helm >=`0.32.0`. The Helm value used to enable/disable transparent
proxy for all applications in a Kubernetes cluster is `connectInject.transparentProxy.defaultEnabled`.

Each Pod for the service will be configured with iptables rules to direct all inbound and outbound traffic through an
inbound and outbound listener on the sidecar proxy. The proxy will be configured to know how to route traffic to the
appropriate upstream services based on [Service
Intentions](/docs/connect/config-entries/service-intentions). This means Connect services no longer
need to use the `consul.hashicorp.com/connect-service-upstreams` annotation to configure upstreams explicitly. Once the
Service Intentions are set, they can simply address the upstream services using KubeDNS.

As of Consul-k8s >= `0.26.0` and Consul-helm >= `0.32.0`, a Kubernetes service that selects application pods is required
for Connect applications, i.e:

```yaml
apiVersion: v1
kind: Service
metadata:
  name: sample-app
  namespace: default
spec:
  selector:
    app: sample-app
  ports:
    - protocol: TCP
      port: 80
```

In the example above, if another service wants to reach `sample-app` via transparent proxying,
it can dial `sample-app.default.svc.cluster.local`, using
[KubeDNS](https://kubernetes.io/docs/concepts/services-networking/dns-pod-service/).
If ACLs with default "deny" policy are enabled, it also needs a
[ServiceIntention](/docs/connect/config-entries/service-intentions) allowing it to talk to
`sample-app`.

### Headless Services
For services that are not addressed using a virtual cluster IP, the upstream service must be
configured using the [DialedDirectly](/docs/connect/config-entries/service-defaults#dialeddirectly) 
option. 

Individual instance addresses can then be discovered using DNS, and dialed through the transparent proxy.
When this mode is enabled on the upstream, connect certificates will be presented for mTLS and
intentions will be enforced at the destination.

Note that when dialing individual instances HTTP routing rules configured with config entries 
will **not** be considered. The transparent proxy acts as a TCP proxy to the original
destination IP address.