Docker Container Networking: Modes, Configuration, and Practical Commands

Docker Container Network Overview

Docker creates three default networks (bridge, host, none) that can be listed with docker network ls . Each container receives a Container‑IP from the docker0 bridge and uses it as the default gateway.

# docker network ls
NETWORK ID   NAME      DRIVER   SCOPE
cd97bb997b84 bridge    bridge   local
0a04824fc9b6 host      host     local
4dcb8fbdb599 none      null     local

Docker's Four Network Modes

Mode

Configuration

Description

host

--network host

Container shares the host's network namespace.

container

--network container:NAME_OR_ID

Container shares another container's network namespace.

none

--network none

Container has its own namespace but no network devices are configured.

bridge

--network bridge (default)

Container connects to the docker0 bridge.

Bridge Mode Details

Docker creates a virtual bridge docker0 on the host. Containers attach to this bridge, receive IPs from its subnet, and can communicate directly via their Container‑IP.

Port mapping is performed with -p which adds DNAT rules in iptables.

# docker run -it --name myapp -p 8080:80 nginx

Container Mode Details

Two containers share the same network namespace, thus the same IP and ports, while file systems remain isolated.

# docker run -dit --name b3 busybox
# docker run -it --name b2 --network container:b3 busybox

Host Mode Details

The container uses the host's network stack directly, gaining the host's IP address and full network performance.

# docker run -it --network host busybox

None Mode Details

Container gets only a loopback interface; no external connectivity unless manually configured.

# docker run -it --network none busybox ifconfig -a

Network Namespace Operations

Linux ip netns commands create isolated namespaces. Example creates namespaces ns0 and ns1 , a veth pair, assigns IPs, and verifies connectivity.

# ip netns add ns0
# ip netns add ns1
# ip link add type veth
# ip link set veth0 netns ns0
# ip link set veth1 netns ns1
# ip netns exec ns0 ip addr add 192.0.0.1/24 dev veth0
# ip netns exec ns1 ip addr add 192.0.0.2/24 dev veth1
# ip netns exec ns0 ping -c 2 192.0.0.2

Common Container Operations

View hostname: hostname

Set custom hostname: --hostname myhost

Specify DNS: --dns 114.114.114.114

Add host entry: --add-host example.com:1.1.1.1

Expose ports with -p (dynamic or fixed).

Custom Bridge Creation

Create a user‑defined bridge with a specific subnet and attach containers to it.

# docker network create -d bridge --subnet 192.168.2.0/24 --gateway 192.168.2.1 mybridge
# docker run -it --network mybridge busybox ifconfig