---
layout: commands
page_title: 'Commands: RTT'
description: |
  The rtt command estimates the network round trip time between two nodes.
---

# Consul RTT

Command: `consul rtt`

Corresponding HTTP API Endpoints: [\[GET\] /v1/coordinate/datacenters](/api-docs/coordinate#read-wan-coordinates), [\[GET\] /v1/coordinate/nodes](/api-docs/coordinate#read-lan-coordinates-for-all-nodes)

The `rtt` command estimates the network round trip time between two nodes using
Consul's network coordinate model of the cluster.

See the [Network Coordinates](/docs/architecture/coordinates) internals guide
for more information on how these coordinates are computed.

The table below shows this command's [required ACLs](/api#authentication). Configuration of
[blocking queries](/api-docs/features/blocking) and [agent caching](/api-docs/features/caching)
are not supported from commands, but may be from the corresponding HTTP endpoint.

| ACL Required            |
| ----------------------- |
| `node:read`<sup>1</sup> |

<p>
  <sup>1</sup> When referencing WAN coordinates, no ACL permission is needed.
</p>

## Usage

Usage: `consul rtt [options] node1 [node2]`

At least one node name is required. If the second node name isn't given, it
is set to the agent's node name. These are the node names as known to
Consul as the `consul members` command would show, not IP addresses.

#### API Options

@include 'http_api_options_client.mdx'

#### Command Options

- `-wan` - Instructs the command to use WAN coordinates instead of LAN
  coordinates. By default, the two nodes are assumed to be nodes in the local
  datacenter and the LAN coordinates are used. If the -wan option is given,
  then the WAN coordinates are used, and the node names must be suffixed by a period
  and the datacenter (eg. "myserver.dc1"). It is not possible to measure between
  LAN coordinates and WAN coordinates, so both nodes must be in the same area.

The following environment variables control accessing the HTTP server via SSL:

- `CONSUL_HTTP_SSL` Set this to enable SSL
- `CONSUL_HTTP_SSL_VERIFY` Set this to disable certificate checking (not recommended)

## Output

If coordinates are available, the command will print the estimated round trip
time between the given nodes:

```shell-session
$ consul rtt n1 n2
Estimated n1 <-> n2 rtt: 0.610 ms (using LAN coordinates)

$ consul rtt n2 # Running from n1
Estimated n1 <-> n2 rtt: 0.610 ms (using LAN coordinates)

$ consul rtt -wan n1.dc1 n2.dc2
Estimated n1.dc1 <-> n2.dc2 rtt: 1.275 ms (using WAN coordinates)
```