Network Settings

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Network Settings

Elasticsearch binds to localhost only by default. This is sufficient for you to run a local development server (or even a development cluster, if you start multiple nodes on the same machine), but you will need to configure some basic network settings in order to run a real production cluster across multiple servers.

Be careful with the network configuration!

Never expose an unprotected node to the public internet.

Commonly Used Network Settings

network.host

The node will bind to this hostname or IP address and publish (advertise) this host to other nodes in the cluster. Accepts an IP address, hostname, a special value, or an array of any combination of these. Note that any values containing a : (e.g., an IPv6 address or containing one of the special values) must be quoted because : is a special character in YAML.

Defaults to _local_.

discovery.seed_hosts

In order to join a cluster, a node needs to know the hostname or IP address of at least some of the other nodes in the cluster. This setting provides the initial list of addresses this node will try to contact. Accepts IP addresses or hostnames. If a hostname lookup resolves to multiple IP addresses then each IP address will be used for discovery. Round robin DNS — returning a different IP from a list on each lookup — can be used for discovery; non- existent IP addresses will throw exceptions and cause another DNS lookup on the next round of pinging (subject to JVM DNS caching).

Defaults to ["127.0.0.1", "[::1]"].

http.port

Port to bind to for incoming HTTP requests. Accepts a single value or a range. If a range is specified, the node will bind to the first available port in the range.

Defaults to 9200-9300.

transport.port

Port to bind for communication between nodes. Accepts a single value or a range. If a range is specified, the node will bind to the first available port in the range.

Defaults to 9300-9400.

Special values for `network.host`

The following special values may be passed to network.host:

`_[networkInterface]_`	Addresses of a network interface, for example `_en0_`.
`_local_`	Any loopback addresses on the system, for example `127.0.0.1`.
`_site_`	Any site-local addresses on the system, for example `192.168.0.1`.
`_global_`	Any globally-scoped addresses on the system, for example `8.8.8.8`.

IPv4 vs IPv6

These special values will work over both IPv4 and IPv6 by default, but you can also limit this with the use of :ipv4 of :ipv6 specifiers. For example, _en0:ipv4_ would only bind to the IPv4 addresses of interface en0.

Discovery in the cloud

More special settings are available when running in the cloud with either the EC2 discovery plugin or the Google Compute Engine discovery plugin installed.

Advanced network settings

The network.host setting explained in Commonly used network settings is a shortcut which sets the bind host and the publish host at the same time. In advanced used cases, such as when running behind a proxy server, you may need to set these settings to different values:

network.bind_host: This specifies which network interface(s) a node should bind to in order to listen for incoming requests. A node can bind to multiple interfaces, e.g. two network cards, or a site-local address and a local address. Defaults to network.host.
network.publish_host: The publish host is the single interface that the node advertises to other nodes in the cluster, so that those nodes can connect to it. Currently an Elasticsearch node may be bound to multiple addresses, but only publishes one. If not specified, this defaults to the “best” address from network.host, sorted by IPv4/IPv6 stack preference, then by reachability. If you set a network.host that results in multiple bind addresses yet rely on a specific address for node-to-node communication, you should explicitly set network.publish_host.

Both of the above settings can be configured just like network.host — they accept IP addresses, host names, and special values.

Advanced TCP Settings

Any component that uses TCP (like the HTTP and Transport modules) share the following settings:

`network.tcp.no_delay`	Enable or disable the TCP no delay setting. Defaults to `true`.
`network.tcp.keep_alive`	Enable or disable TCP keep alive. Defaults to `true`.
`network.tcp.reuse_address`	Should an address be reused or not. Defaults to `true` on non-windows machines.
`network.tcp.send_buffer_size`	The size of the TCP send buffer (specified with size units). By default not explicitly set.
`network.tcp.receive_buffer_size`	The size of the TCP receive buffer (specified with size units). By default not explicitly set.

Transport and HTTP protocols

An Elasticsearch node exposes two network protocols which inherit the above settings, but may be further configured independently:

TCP Transport: Used for communication between nodes in the cluster, by the Java Transport client. See the Transport module for more information.
HTTP: Exposes the JSON-over-HTTP interface used by all clients other than the Java clients. See the HTTP module for more information.

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