Docker: learn about docker network and customized docker network card

docker network

Understanding docker network

Test ip addr view

We can test whether the container can ping between containers

# Run a tomcat 
docker run -d -P --name tomcat01 tomcat
# Get ip
ip addr

# We can view the ip address of the container by viewing the metadata

# Then ping the container with the host linux
 # Nengtong


  1. Every time we start a docker container, docker will assign an ip address to each of our containers
  2. As long as we install docker, we will have a network card docker0 bridging mode, using evth pair technology

Our newly started container will have a new network card

We found that the network cards of these containers are one-to-one

# We found that the network card brought by this container is a pair
# Veth pair is a pair of virtual device interfaces. They all appear in pairs. One end is connected to the protocol and the other end is connected to each other
# Because of this feature, Veth pair acts as a bridge to connect various virtual network devices
# The links between OpenStac, Docker containers and OVS all use Veth pair technology

Let's create a new tomcat and try to ping between containers

Conclusion: containers can ping each other!

Draw a network model diagram

Conclusion: tomcat01 and tomcat02 share the same router, docker0

When all containers do not specify a network, they are routed by docker0. doucker will assign a default available IP to our containers


Docker uses the Linux bridge, and the host is a docker container bridge docker0

All network interfaces in Docker are virtual, and virtual forwarding efficiency is high! (transfer files via intranet!)

As long as the container is deleted, there will be no corresponding bridge pair!


Considering a scenario, we write a micro service, database url =ip; The project does not restart, but the data ip is replaced. We hope to solve this problem and access the container by name

[root@iZ2zeg4ytp0whqtmxbsqiiZ ~]# docker exec -it tomcat02 ping tomcat01
ping: tomcat01: Name or service not known
# How can it be solved?
# The problem of network connectivity can be solved through -- link
[root@iZ2zeg4ytp0whqtmxbsqiiZ ~]# docker run -d -P  --name tomcat03 --link tomcat02 tomcat
[root@iZ2zeg4ytp0whqtmxbsqiiZ ~]# docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS                     NAMES
3a2bcaba804c        tomcat              " run"   4 seconds ago       Up 3 seconds>8080/tcp   tomcat03
f22ed47ed1be        tomcat              " run"   57 minutes ago      Up 57 minutes>8080/tcp   tomcat02
9d97f93401a0        tomcat              " run"   About an hour ago   Up About an hour>8080/tcp   tomcat01
[root@iZ2zeg4ytp0whqtmxbsqiiZ ~]# docker exec -it tomcat03 ping tomcat02
PING tomcat02 ( 56(84) bytes of data.
64 bytes from tomcat02 ( icmp_seq=1 ttl=64 time=0.129 ms
64 bytes from tomcat02 ( icmp_seq=2 ttl=64 time=0.100 ms
64 bytes from tomcat02 ( icmp_seq=3 ttl=64 time=0.110 ms
64 bytes from tomcat02 ( icmp_seq=4 ttl=64 time=0.107 ms
# Can reverse ping pass?
[root@iZ2zeg4ytp0whqtmxbsqiiZ ~]# docker exec -it tomcat02 ping tomcat03
ping: tomcat03: Name or service not known

Explore: inspect!

In fact, this tomcat03 is configured with tomcat02 locally?

[root@iZ2zeg4ytp0whqtmxbsqiiZ ~]# docker exec -it tomcat03 cat /etc/hosts   localhost
::1 localhost ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters  tomcat02 f22ed47ed1be  3a2bcaba804c

Essence: the – link is that we added a tomcat02 f22ed47ed1be in the hosts configuration

We don't recommend using – link now when we play Docker!

Custom network! Docker0 is not used!

Problem with Docker0: it does not support container name link access!

Custom network

View all docker networks

Network mode

Bridge: bridge mode. By default, bridge docker is created in brdge mode

none: do not configure the network

Host: share network with host

Container: the container is connected to the network! (less use, very limited)


# The command we start directly has a -- net bridge by default, and this is our docker0
docker run -d -P --name tomcat01 tomcat
docker run -d -P --name tomcat01 --net bridge tomcat
# docker0 feature. By default, the container name cannot be accessed, - link can open the connection!
# We can customize a network!
# --driver bridge
# --subnet can support 255 * 255 networks ~
# --gateway
[root@iZ2zeg4ytp0whqtmxbsqiiZ ~]# docker network create --driver bridge --subnet --gateway mynet
[root@iZ2zeg4ytp0whqtmxbsqiiZ ~]# docker network ls
NETWORK ID          NAME                DRIVER              SCOPE
30d601788862        bridge              bridge              local
226019b14d91        host                host                local
26a5afdf4805        mynet               bridge              local
7496c014f74b        none                null                local

The network we created is ok!

Start two containers in the network you created

[root@iZ2zeg4ytp0whqtmxbsqiiZ ~]# docker run -d -P --name tomcat-net-01 --net mynet tomcat
[root@iZ2zeg4ytp0whqtmxbsqiiZ ~]# docker run -d -P --name tomcat-net-02 --net mynet tomcat
[root@iZ2zeg4ytp0whqtmxbsqiiZ ~]# docker network inspect mynet
        "Name": "mynet",
        "Id": "26a5afdf4805d7ee0a660b82244929a4226470d99a179355558dca35a2b983ec",
        "Created": "2020-08-14T11:12:40.553433163+08:00",
        "Scope": "local",
        "Driver": "bridge",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": {},
            "Config": [
                    "Subnet": "",
                    "Gateway": ""
        "Internal": false,
        "Attachable": false,
        "Ingress": false,
        "ConfigFrom": {
            "Network": ""
        "ConfigOnly": false,
        "Containers": {
            "0e85ebe6279fd23379d39b27b5f47c1e18f23ba7838637802973bf6449e22f5c": {
                "Name": "tomcat-net-01",
                "EndpointID": "576ce5c0f5860a5aab5e487a805da9d72f41a409c460f983c0bd341dd75d83ac",
                "MacAddress": "02:42:c0:a8:00:02",
                "IPv4Address": "",
                "IPv6Address": ""
            "c6e462809ccdcebb51a4078b1ac8fdec33f1112e9e416406b606d0c9fb6f21b5": {
                "Name": "tomcat-net-02",
                "EndpointID": "81ecbc4fe26e49855fe374f2d7c00d517b11107cc91a174d383ff6be37d25a30",
                "MacAddress": "02:42:c0:a8:00:03",
                "IPv4Address": "",
                "IPv6Address": ""
        "Options": {},
        "Labels": {}

# Join again

[root@iZ2zeg4ytp0whqtmxbsqiiZ ~]# docker exec -it tomcat-net-01 ping
PING ( 56(84) bytes of data.
64 bytes from icmp_seq=1 ttl=64 time=0.113 ms
64 bytes from icmp_seq=2 ttl=64 time=0.093 ms
--- ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 999ms
rtt min/avg/max/mdev = 0.093/0.103/0.113/0.010 ms

# Now you can ping the name without -- link!

[root@iZ2zeg4ytp0whqtmxbsqiiZ ~]# docker exec -it tomcat-net-01 ping tomcat-net-02
PING tomcat-net-02 ( 56(84) bytes of data.
64 bytes from tomcat-net-02.mynet ( icmp_seq=1 ttl=64 time=0.068 ms
64 bytes from tomcat-net-02.mynet ( icmp_seq=2 ttl=64 time=0.096 ms
64 bytes from tomcat-net-02.mynet ( icmp_seq=3 ttl=64 time=0.094 ms

Our custom network docker They have helped us maintain the corresponding relationship. It is recommended that we use the network in this way


redis - Different clusters use different networks to ensure the safety and health of the cluster

mysql - Different clusters use different networks to ensure the safety and health of the cluster

Network connectivity

Test to get through tomcat01 and mynet

# Connected ok
[root@iZ2zeg4ytp0whqtmxbsqiiZ ~]# docker exec -it tomcat01 ping tomcat-net-01
PING tomcat-net-01 ( 56(84) bytes of data.
64 bytes from tomcat-net-01.mynet ( icmp_seq=1 ttl=64 time=0.100 ms
64 bytes from tomcat-net-01.mynet ( icmp_seq=2 ttl=64 time=0.085 ms
--- tomcat-net-01 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1000ms
rtt min/avg/max/mdev = 0.085/0.092/0.100/0.012 ms
# Still unable to connect, no connect
[root@iZ2zeg4ytp0whqtmxbsqiiZ ~]# docker exec -it tomcat02 ping tomcat-net-01
ping: tomcat-net-01: Name or service not known

Conclusion: if you want to operate others across the network, you should use docker network connect to connect!

Tags: Linux Docker network

Posted on Sun, 07 Nov 2021 14:37:01 -0500 by bufke