[[modules-network]]
== Basic Settings

Commonly used network settings:

[cols="<,<",options="header",]
|=======================================================================
|Name |Description
|`network.host` |Host to bind and publish to other nodes. Can be set to an IP address, hostname, or special value (see table below). Defaults to `_local_`.

|`discovery.zen.ping.unicast.hosts`|Initial list other nodes. Can be set to IP addresses or hostnames. Defaults to `["127.0.0.1", "[::1]"]`.

|`http.port` |Port to bind for incoming http requests. Can be set to a single value or a range. Defaults to `9200-9300`.

|`transport.tcp.port` |Port to bind for communication between nodes. Can be set to a single value or a range. Defaults to `9300-9400`.
|=======================================================================

Be careful with network configuration! Never expose an unprotected instance
to the public internet.

[cols="<,<",options="header",]
|=======================================================================
|Special Host Value |Description
|`_[networkInterface]_` |Resolves to the addresses of the provided
network interface. For example `_en0_`.

|`_local_` |Will be resolved to loopback addresses (e.g. 127.0.0.1)

|`_site_` |Will be resolved to site-local addresses (e.g. 192.168.0.1)

|`_global_` |Will be resolved to globally-scoped addresses (e.g. 8.8.8.8)
|=======================================================================

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`.

When the `discovery-ec2` plugin is installed, you can use
{plugins}/discovery-ec2-discovery.html#discovery-ec2-network-host[ec2 specific host settings].

When the `discovery-gce` plugin is installed, you can use
{plugins}/discovery-gce-network-host.html[gce specific host settings].

[float]
[[advanced]]
=== Advanced network settings

`network.bind_host` and `network.publish_host` can be set instead of `network.host` 
for advanced cases such as when behind a proxy server.

The `network.bind_host` setting allows to control the host different network
components will bind on. By default, the bind host will be `_local_`
(loopback addresses such as `127.0.0.1`, `::1`).

The `network.publish_host` setting allows to control the host the node will
publish itself within the cluster so other nodes will be able to 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.bind_host`, sorted by IPv4/IPv6 stack preference, then by reachability.

Both settings allows to be configured with either explicit host address(es)
or host name(s). The settings also accept logical setting value(s) explained
in the following table:

[float]
[[tcp-settings]]
=== Advanced TCP Settings

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

[cols="<,<",options="header",]
|=======================================================================
|Setting |Description
|`network.tcp.no_delay` |Enable or disable 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 size
(in size setting format). By default not explicitly set.

|`network.tcp.receive_buffer_size` |The size of the tcp receive buffer
size (in size setting format). By default not explicitly set.
|=======================================================================

[float]
[[module-settings]]
=== Module-specific Settings

There are several modules within a Node that use network based
configuration, for example, the
<<modules-transport,transport>> and
<<modules-http,http>> modules. Node level
network settings allows to set common settings that will be shared among
all network based modules (unless explicitly overridden in each module).