New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Document new DOCKER-USER iptables chain #3554

Merged
merged 2 commits into from Jun 13, 2017
Merged
Changes from all commits
Commits
File filter...
Filter file types
Jump to…
Jump to file or symbol
Failed to load files and symbols.
+32 −1
Diff settings

Always

Just for now

@@ -1,6 +1,6 @@
---
description: How do we connect docker containers within and across hosts ?
keywords: Examples, Usage, network, docker, documentation, user guide, multihost, cluster
keywords: network, networking, iptables, user-defined networks, bridge, firewall, ports
redirect_from:
- /engine/userguide/networking/dockernetworks/
- /articles/networking/
@@ -12,6 +12,9 @@ including the type of networks created by default and how to create your own
user-defined networks. It also describes the resources required to create
networks on a single host or across a cluster of hosts.

For details about how Docker interacts with `iptables` on Linux hosts, see
[Docker and `iptables`](#docker-and-iptables).

## Default Networks

When you install Docker, it creates three networks automatically. You can list
@@ -550,6 +553,34 @@ in default `bridge` network and the
[linking containers in user-defined networks](work-with-networks.md#linking-containers-in-user-defined-networks)
for links functionality in user-defined networks.

## Docker and iptables

Linux hosts use a kernel module called `iptables` to manage access to network
devices, including routing, port forwarding, network address translation (NAT),
and other concerns. Docker modifies `iptables` rules when you start or stop
containers which publish ports, when you create or modify networks or attach
containers to them, or for other network-related operations.

Full discussion of `iptables` is out of scope for this topic. To see which
`iptables` rules are in effect at any time, you can use `iptables -L`. Multiple
tables exist, and you can list a specific table, such as `nat`, `prerouting`, or
`postrouting`, using a command such as `iptables -t nat -L`. For full
documentation about `iptables`, see
[netflilter/iptables](https://netfilter.org/documentation/){: target="_blank" class="_" }.

Typically, `iptables` rules are created by an initialization script or a daemon
process such as `firewalld`. The rules do not persist across a system reboot, so
the script or utility must run when the system boots, typically at run-level 3
or directly after the network is initialized. Consult the networking
documentation for your Linux distribution for suggestions about the appropriate
way to make `iptables` rules persistent.

Docker dynamically manages `iptables` rules for the daemon, as well as your
containers, services, and networks. In Docker 17.06 and higher, you can add
rules to a new table called `DOCKER-USER`, and these rules will be loaded before
any rules Docker creates automatically. This can be useful if you need to
pre-populate `iptables` rules that need to be in place before Docker runs.

## Related information

- [Work with network commands](work-with-networks.md)
ProTip! Use n and p to navigate between commits in a pull request.