---
layout: docs
page_title: TCP - Listeners - Configuration
description: |-
  The TCP listener configures Vault to listen on the specified TCP address and
  port.
---

# `tcp` listener

The TCP listener configures Vault to listen on a TCP address/port.

```hcl
listener "tcp" {
  address = "127.0.0.1:8200"
}
```

The `listener` stanza may be specified more than once to make Vault listen on
multiple interfaces. If you configure multiple listeners you also need to
specify [`api_addr`][api-addr] and [`cluster_addr`][cluster-addr] so Vault will
advertise the correct address to other nodes.

## Listener's custom response headers

As of version 1.9, Vault supports defining custom HTTP response headers for the root path (`/`) and also on API endpoints (`/v1/*`).
The headers are defined based on the returned status code. For example, a user can define a list of
custom response headers for the `200` status code, and another list of custom response headers for
the `307` status code. There is a `"/sys/config/ui"` [API endpoint](/vault/api-docs/system/config-ui) which allows users
to set `UI` specific custom headers. If a header is configured in a configuration file, it is not allowed
to be reconfigured through the `"/sys/config/ui"` [API endpoint](/vault/api-docs/system/config-ui). In cases where a
custom header value needs to be modified or the custom header needs to be removed, the Vault's configuration file
needs to be modified accordingly, and a `SIGHUP` signal needs to be sent to the Vault process.

If a header is defined in the configuration file and the same header is used by the internal
processes of Vault, the configured header is not accepted. For example, a custom header which has
the `X-Vault-` prefix will not be accepted. A message will be logged in the Vault's logs
upon start up indicating the header with `X-Vault-` prefix is not accepted.

### Order of precedence

If the same header is configured in both the configuration file and
in the `"/sys/config/ui"` [API endpoint](/vault/api-docs/system/config-ui), the header in the configuration file takes precedence.
For example, the `"Content-Security-Policy"` header is defined by default in the
`"/sys/config/ui"` [API endpoint](/vault/api-docs/system/config-ui). If that header is also defined in the configuration file,
the value in the configuration file is set in the response headers instead of the
default value in the `"/sys/config/ui"` [API endpoint](/vault/api-docs/system/config-ui).

## `tcp` listener parameters

- `address` `(string: "127.0.0.1:8200")` – Specifies the address to bind to for
  listening. This can be dynamically defined with a
  [go-sockaddr template](https://pkg.go.dev/github.com/hashicorp/go-sockaddr/template)
  that is resolved at runtime.

- `cluster_address` `(string: "127.0.0.1:8201")` – Specifies the address to bind
  to for cluster server-to-server requests. This defaults to one port higher
  than the value of `address`. This does not usually need to be set, but can be
  useful in case Vault servers are isolated from each other in such a way that
  they need to hop through a TCP load balancer or some other scheme in order to
  talk. This can be dynamically defined with a
  [go-sockaddr template](https://pkg.go.dev/github.com/hashicorp/go-sockaddr/template)
  that is resolved at runtime.

- `chroot_namespace` `(string: "")` – Specifies an alternate top-level namespace
  for the listener. Vault appends namespaces provided in the `X-Vault-Namespace`
  header or the `-namespace` field in a CLI command to the top-level namespace
  to determine the full namespace path for the request. For example, if
  `chroot_namespace` is set to `admin` and the `X-Vault-Namespace` header is
  `ns1`, the full namespace path is `admin/ns1`. Calls to the listener will fail
   with a 4XX error if the top-level namespace provided for `chroot_namespace`
   does not exist.
- `http_idle_timeout` `(string: "5m")` - Specifies the maximum amount of time to
  wait for the next request when keep-alives are enabled. If `http_idle_timeout`
  is zero, the value of `http_read_timeout` is used. If both are zero, the value
  of `http_read_header_timeout` is used. This is specified using a label suffix
  like `"30s"` or `"1h"`.

- `http_read_header_timeout` `(string: "10s")` - Specifies the amount of time
  allowed to read request headers. This is specified using a label suffix like
  `"30s"` or `"1h"`.

- `http_read_timeout` `(string: "30s")` - Specifies the maximum duration for
  reading the entire request, including the body. This is specified using a
  label suffix like `"30s"` or `"1h"`.

- `http_write_timeout` `string: "0")` - Specifies the maximum duration before
  timing out writes of the response and is reset whenever a new request's header
  is read. The default value of `"0"` means infinity. This is specified using a
  label suffix like `"30s"` or `"1h"`.

- `max_request_size` `(int: 33554432)` – Specifies a hard maximum allowed
  request size, in bytes. Defaults to 32 MB if not set or set to `0`.
  Specifying a number less than `0` turns off limiting altogether.

- `max_request_duration` `(string: "90s")` – Specifies the maximum
  request duration allowed before Vault cancels the request. This overrides
  `default_max_request_duration` for this listener.

- `proxy_protocol_behavior` `(string: "")` – When specified, enables a PROXY
  protocol version 1 behavior for the listener.
  Accepted Values:

  - _use_always_ - The client's IP address will always be used.
  - _allow_authorized_ - If the source IP address is in the
    `proxy_protocol_authorized_addrs` list, the client's IP address will be used.
    If the source IP is not in the list, the source IP address will be used.
  - _deny_unauthorized_ - The traffic will be rejected if the source IP
    address is not in the `proxy_protocol_authorized_addrs` list.

- `proxy_protocol_authorized_addrs` `(string: <required-if-enabled> or array: <required-if-enabled> )` –
  Specifies the list of allowed source IP addresses to be used with the PROXY protocol.
  Not required if `proxy_protocol_behavior` is set to `use_always`. Source IPs should
  be comma-delimited if provided as a string. At least one source IP must be provided,
  `proxy_protocol_authorized_addrs` cannot be an empty array or string.

- `tls_disable` `(string: "false")` – Specifies if TLS will be disabled. Vault
  assumes TLS by default, so you must explicitly disable TLS to opt-in to
  insecure communication.

- `tls_cert_file` `(string: <required-if-enabled>, reloads-on-SIGHUP)` –
  Specifies the path to the certificate for TLS. It requires a PEM-encoded file.
  To configure the listener to use a CA certificate, concatenate the primary certificate and the CA
  certificate together. The primary certificate should appear first in the
  combined file. On `SIGHUP`, the path set here _at Vault startup_ will be used
  for reloading the certificate; modifying this value while Vault is running
  will have no effect for `SIGHUP`s.

- `tls_key_file` `(string: <required-if-enabled>, reloads-on-SIGHUP)` –
  Specifies the path to the private key for the certificate. It requires a PEM-encoded file.
  If the key file is encrypted, you will be prompted to enter the passphrase on server startup.
  The passphrase must stay the same between key files when reloading your
  configuration using `SIGHUP`. On `SIGHUP`, the path set here _at Vault
  startup_ will be used for reloading the certificate; modifying this value
  while Vault is running will have no effect for `SIGHUP`s.

- `tls_min_version` `(string: "tls12")` – Specifies the minimum supported
  version of TLS. Accepted values are "tls10", "tls11", "tls12" or "tls13".

  ~> **Warning**: TLS 1.1 and lower (`tls10` and `tls11` values for the
  `tls_min_version` and `tls_max_version` parameters) are widely considered
  insecure.

- `tls_max_version` `(string: "tls13")` – Specifies the maximum supported
  version of TLS. Accepted values are "tls10", "tls11", "tls12" or "tls13".

~> **Warning**: TLS 1.1 and lower (`tls10` and `tls11` values for the
  `tls_min_version` and `tls_max_version` parameters) are widely considered
  insecure.

- `tls_cipher_suites` `(string: "")` – Specifies the list of supported
  ciphersuites as a comma-separated-list. The list of all available ciphersuites
  is available in the [Golang TLS documentation][golang-tls].

  ~> **Note**: Go only consults the `tls_cipher_suites` list for TLSv1.2 and
  earlier; the order of ciphers is not important. For this parameter to be
  effective, the `tls_max_version` property must be set to `tls12` to prevent
  negotiation of TLSv1.3, which is not recommended. For more information about
  this and other TLS related changes, see the [Go TLS blog post][go-tls-blog].

- `tls_prefer_server_cipher_suites` `(string: "false")` – Specifies to prefer the
  server's ciphersuite over the client ciphersuites.

  ~> **Warning**: The `tls_prefer_server_cipher_suites` parameter is
  deprecated. Setting it has no effect. See the above
  [Go blog post][go-tls-blog] for more information about
  this change.

- `tls_require_and_verify_client_cert` `(string: "false")` – Turns on client
  authentication for this listener; the listener will require a presented
  client cert that successfully validates against system CAs.

- `tls_client_ca_file` `(string: "")` – PEM-encoded Certificate Authority file
  used for checking the authenticity of client.

- `tls_disable_client_certs` `(string: "false")` – Turns off client
  authentication for this listener. The default behavior (when this is false)
  is for Vault to request client certificates when available.

  ~> **Warning**: The `tls_disable_client_certs` and `tls_require_and_verify_client_cert` fields in the listener stanza of the Vault server configuration are mutually exclusive fields. Please ensure they are not both set to true. TLS client verification remains optional with default settings and is not enforced.

- `x_forwarded_for_authorized_addrs` `(string: <required-to-enable>)` –
  Specifies the list of source IP CIDRs for which an X-Forwarded-For header
  will be trusted. Comma-separated list or JSON array. This turns on
  X-Forwarded-For support.  If for example Vault receives connections from the
  load balancer's IP of `1.2.3.4`, adding `1.2.3.4` to `x_forwarded_for_authorized_addrs`
  will result in the `remote_address` field in the audit log being populated with the
  connecting client's IP, for example `3.4.5.6`. Note this requires the load balancer
  to send the connecting client's IP in the `X-Forwarded-For` header.

- `x_forwarded_for_hop_skips` `(string: "0")` – The number of addresses that will be
  skipped from the _rear_ of the set of hops. For instance, for a header value
  of `1.2.3.4, 2.3.4.5, 3.4.5.6, 4.5.6.7`, if this value is set to `"1"`, the address that
  will be used as the originating client IP is `3.4.5.6`.

- `x_forwarded_for_reject_not_authorized` `(string: "true")` – If set false,
  if there is an X-Forwarded-For header in a connection from an unauthorized
  address, the header will be ignored and the client connection used as-is,
  rather than the client connection rejected.

- `x_forwarded_for_reject_not_present` `(string: "true")` – If set false, if
  there is no X-Forwarded-For header or it is empty, the client address will be
  used as-is, rather than the client connection rejected.

### `telemetry` parameters

- `unauthenticated_metrics_access` `(bool: false)` - If set to true, allows
  unauthenticated access to the `/v1/sys/metrics` endpoint.

### `profiling` parameters

- `unauthenticated_pprof_access` `(bool: false)` - If set to true, allows
  unauthenticated access to the `/v1/sys/pprof` endpoint.

### `inflight_requests_logging` parameters

- `unauthenticated_in_flight_requests_access` `(bool: false)` - If set to true, allows
  unauthenticated access to the `/v1/sys/in-flight-req` endpoint.

### `custom_response_headers` parameters

- `default` `(key-value-map: {})` - A map of string header names to an array of
  string values. The default headers are set on all endpoints regardless of
  the status code value. For an example, please refer to the
  "Configuring custom http response headers" section.

- `<specific status code>` `(key-value-map: {})` - A map of string header names
  to an array of string values. These headers are set only when the specific status
  code is returned. For example, `"200" = {"Header-A": ["Value1", "Value2"]}`, `"Header-A"`
  is set when the http response status code is `"200"`.

- `<collective status code>` `(key-value-map: {})` - A map of string header names
  to an array of string values. These headers are set only when the response status
  code falls under the collective status code.
  For example, `"2xx" = {"Header-A": ["Value1", "Value2"]}`, `"Header-A"`
  is set when the http response status code is `"200"`, `"204"`, etc.

## `tcp` listener examples

### Configuring TLS

This example shows enabling a TLS listener.

```hcl
listener "tcp" {
  tls_cert_file = "/etc/certs/vault.crt"
  tls_key_file  = "/etc/certs/vault.key"
}
```

### Listening on multiple interfaces

This example shows Vault listening on a private interface, as well as localhost.

```hcl
listener "tcp" {
  address = "127.0.0.1:8200"
}

listener "tcp" {
  address = "10.0.0.5:8200"
}

# Advertise the non-loopback interface
api_addr = "https://10.0.0.5:8200"
cluster_addr = "https://10.0.0.5:8201"
```

### Configuring unauthenticated metrics access

This example shows enabling unauthenticated metrics access.

```hcl
listener "tcp" {
  telemetry {
    unauthenticated_metrics_access = true
  }
}
```

### Configuring unauthenticated profiling access

This example shows enabling unauthenticated profiling access.

```hcl
listener "tcp" {
  profiling {
    unauthenticated_pprof_access = true
    unauthenticated_in_flight_request_access = true
  }
}
```

### Configuring custom http response headers

Note: Requires Vault version 1.9 or newer. This example shows configuring custom http response headers.
Operators can configure `"custom_response_headers"` sub-stanza in the listener stanza to set custom http
headers appropriate to their applications. Examples of such headers are `"Strict-Transport-Security"`
and `"Content-Security-Policy"` which are known HTTP headers, and could be configured to harden
the security of an application communicating with the Vault endpoints. Note that vulnerability
scans often examine such security related HTTP headers. In addition, application specific
custom headers can also be configured. For example, `"X-Custom-Header"` has been configured
in the example below.

```hcl
listener "tcp" {
  custom_response_headers {
    "default" = {
      "Strict-Transport-Security" = ["max-age=31536000","includeSubDomains"],
      "Content-Security-Policy" = ["connect-src https://clusterA.vault.external/"],
      "X-Custom-Header" = ["Custom Header Default Value"],
    },
    "2xx" = {
      "Content-Security-Policy" = ["connect-src https://clusterB.vault.external/"],
      "X-Custom-Header" = ["Custom Header Value 1", "Custom Header Value 2"],
    },
    "301" = {
      "Strict-Transport-Security" = ["max-age=31536000"],
      "Content-Security-Policy" = ["connect-src https://clusterC.vault.external/"],
    },
  }
}
```

In situations where a header is defined under several status code subsections,
the header matching the most specific response code will be returned. For example,
with the config example below, a `307` response would return `307 Custom header value`,
while a `306` would return `3xx Custom header value`.

```hcl
listener "tcp" {
  custom_response_headers {
    "default" = {
       "X-Custom-Header" = ["default Custom header value"]
    },
    "3xx" = {
       "X-Custom-Header" = ["3xx Custom header value"]
    },
    "307" = {
       "X-Custom-Header" = ["307 Custom header value"]
    }
  }
}
```

### Listening on all IPv6 & IPv4 interfaces

This example shows Vault listening on all IPv4 & IPv6 interfaces including localhost.

```hcl
listener "tcp" {
  address         = "[::]:8200"
  cluster_address = "[::]:8201"
}
```

### Listening to specific IPv6 address

This example shows Vault only using IPv6 and binding to the interface with the IP address: `2001:1c04:90d:1c00:a00:27ff:fefa:58ec`

```hcl
listener "tcp" {
  address         = "[2001:1c04:90d:1c00:a00:27ff:fefa:58ec]:8200"
  cluster_address = "[2001:1c04:90d:1c00:a00:27ff:fefa:58ec]:8201"
}

# Advertise the non-loopback interface
api_addr = "https://[2001:1c04:90d:1c00:a00:27ff:fefa:58ec]:8200"
cluster_addr = "https://[2001:1c04:90d:1c00:a00:27ff:fefa:58ec]:8201"
```

[golang-tls]: https://golang.org/src/crypto/tls/cipher_suites.go
[api-addr]: /vault/docs/configuration#api_addr
[cluster-addr]: /vault/docs/configuration#cluster_addr
[go-tls-blog]: https://go.dev/blog/tls-cipher-suites
