consul/website/content/docs/connect/proxies/envoy-extensions/usage/property-override.mdx

---
layout: docs
page_title: Configure Envoy proxy properties
description: Learn how to use the property-override extension for Envoy proxies to set and remove individual properties for the Envoy resources Consul generates.
---

# Configure Envoy proxy properties

This topic describes how to use the `property-override` extension to set and remove individual properties for the Envoy resources Consul generates. The extension uses the [protoreflect](https://pkg.go.dev/google.golang.org/protobuf/reflect/protoreflect), which enables Consul to dynamically manipulate messages.

## Workflow

- Complete the following steps to use the `property-override` extension:
- Configure an `EnvoyExtensions` block in a service defaults or proxy defaults configuration entry. 
- Apply the configuration entry.

!> **Security warning**: The property override extension is an advanced feature capable of introducing unintended consequences or reducing cluster security if used incorrectly. Consul does not enforce TLS retention, intentions, or other security-critical components of the Envoy configuration. Additionally, Consul does not verify that the configuration does not contain errors that affect service traffic.

## Add the `EnvoyExtensions`

Add Envoy extension configurations to a proxy defaults or service defaults configuration entry. Place the extension configuration in an `EnvoyExtensions` block in the configuration entry.

- When you configure Envoy extensions on proxy defaults, they apply to every service.
- When you configure Envoy extensions on service defaults, they apply to a specific service.

Consul applies Envoy extensions configured in proxy defaults before it applies extensions in service defaults. As a result, the Envoy extension configuration in service defaults may  override configurations in proxy defaults.

In the following service defaults configuration entry example, Consul adds a new `/upstream_connection_options/tcp_keepalive/keepalive_probes-5` field to each of the proxy's cluster configuration for the outbound `db`service upstream. The configuration applies to all `connect-proxy` proxies with services configured to communicate over HTTP:

<Tabs>
<Tab heading="HCL" group="hcl">
<CodeBlockConfig filename="property-override-extension-service-defaults.hcl">

```hcl
Kind     = "service-defaults"
Name     = "global"
Protocol = "http"
EnvoyExtensions = [ 
  {
    Name = "builtin/property-override"
    Arguments = {
      ProxyType = "connect-proxy"
      Patches = [
        {
          ResourceFilter  = {
            ResourceType     = "cluster"
            TrafficDirection = "outbound"
            Services = [{
               Name =  "other-svc"
            }]
          }
          Op    = "add"
          Path  = "/upstream_connection_options/tcp_keepalive/keepalive_probes"
          Value = 5
        }
      ]
    }
  }
]
```
</CodeBlockConfig>
</Tab>

<Tab heading="JSON" group="json">
<CodeBlockConfig filename="property-override-extension-service-defaults.json">

```json
"kind": "service-defaults",
"name": "global",
"protocol": "http",
"envoy_extensions": [{
  "name": "builtin/property-override",
  "arguments": {
    "proxyType": "connect-proxy",
    "patches": [{
      "resourceFilter": {
        "resourceType": "cluster", 
        "trafficDirection": "outbound",
        "services": [{ "name":  "other-svc" }],
        "op": "add",
        "path": "/upstream_connection_options/tcp_keepalive/keepalive_probes",
        "value": 5
       }
    }]
  }
}]
```
</CodeBlockConfig>
</Tab>
<Tab heading="Kubernetes" group="kubernetes">
<CodeBlockConfig filename="property-override-extension-proxy-defaults.yaml">

```yaml
apiversion: consul.hashicorp.com/v1alpha1
kind: ServiceDefaults
metadata:
  name: global
spec:
  protocol: http
  envoyExtensions:
    name = "builtin/property-override"
    arguments: 
      proxyType: "connect-proxy",
      patches: 
      - resourceFilter: 
          resourceType: "cluster" 
          trafficDirection: "outbound"
          services: 
            - name:  "other-svc"
        op: "add"
        path: "/upstream_connection_options/tcp_keepalive/keepalive_probes",
        value: 5
```

</CodeBlockConfig>
</Tab>
</Tabs>


Refer to the [property override configuration reference](/consul/docs/connect/proxies/envoy-extensions/configuration/property-override) for details on how to configure the extension. 

Refer to the [proxy defaults configuration entry reference](/consul/docs/connect/config-entries/proxy-defaults) and [service defaults configuration entry reference](/consul/docs/connect/config-entries/service-defaults) for details on how to define the configuration entries. 

!> **Warning:** Adding Envoy extensions default proxy configurations may have unintended consequences. We recommend configuring `EnvoyExtensions` in service defaults configuration entries in most cases.

### Constructing paths

To target the properties for an Envoy resource type, you must specify the path where the properties exist in the [`Path` field](/consul/docs/connect/proxies/envoy-extensions/configuration/property-override#patches-path) of the property override extension configuration. Set the `Path` field to an empty or partially invalid string when saving the configuration entry and Consul returns an error with a list of supported fields for the first unrecognized segment of the path. By default, Consul only returns the first ten fields, but you can set the [`Debug` field](/consul/docs/connect/proxies/envoy-extensions/configuration/property-override#debug) to `true`  to direct Consul to output all possible fields. 

In the following example, Consul outputs the top-level fields available for the Envoy cluster resource:

```hcl
Kind = "service-defaults"
Name = "api"
EnvoyExtensions = [
  {
    Name = "builtin/property-override"
    Arguments = {
      ProxyType = "connect-proxy"
      Patches = [
        {
          ResourceFilter = {
            ResourceType = "cluster"
            TrafficDirection = "outbound"
          }
          Op = "add"
          Path =  ""
          Value =  5
         }
      ]
    }
  }
]
```

After applying the configuration entry, Consul prints a message that includes the possible fields for the resource:

```shell-session
$ consul config write api.hcl
non-empty, non-root Path is required. available cluster fields:
/outlier_detection
/outlier_detection/enforcing_consecutive_5xx
/outlier_detection/failure_percentage_request_volume
/round_robin_lb_config
/round_robin_lb_config/slow_start_config
```

You can use the output to help you construct the appropriate value for the `Path` field. For example:

```shell-session
$ consul config write api.hcl | grep round_robin
/round_robin_lb_config
```




## Apply the configuration entry

If your network is deployed to virtual machines, use the `consul config write` command and specify the proxy defaults or service defaults configuration entry to apply the configuration. For Kubernetes-orchestrated networks, use the `kubectl apply` command. The following example applies the extension in a proxy defaults configuration entry.

<Tabs>
<Tab heading="HCL" group="hcl">

```shell-session
$ consul config write property-override-extension-service-defaults.hcl
```

</Tab>
<Tab heading="JSON" group="json">

```shell-session
$ consul config write property-override-extension-service-defaults.json

```

</Tab>
<Tab heading="Kubernetes" group="kubernetes">

```shell-session
$ kubectl apply property-override-extension-service-defaults.yaml
```

</Tab>
</Tabs>