Let’s learn Docker Networking….
There are majorly five networks in docker – bridge, host, overlay, none, and macvlan.
Bridge network is the default network in docker. An introduction to these networks has been given in my previous article on docker architecture.
In this article, I will show you the practical part of docker networking. You will get to know how you can check your docker network details, how to connect to a network, how to create your network, and more. So, let’s get started.
Whenever you run a docker container, a default bridge network call docker0 gets associated with the container unless any other network is specified. For example, when I run ifconfig command, you will get the details of docker0 network of bridge type along with other network details.
osboxes@worker2:~$ ifconfig
docker0: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500
inet 172.17.0.1 netmask 255.255.0.0 broadcast 172.17.255.255
ether 02:42:f6:59:4a:5f txqueuelen 0 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
enp0s3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 10.0.2.15 netmask 255.255.255.0 broadcast 10.0.2.255
inet6 fe80::763e:c0b4:14df:b273 prefixlen 64 scopeid 0x20<link>
ether 08:00:27:68:64:9a txqueuelen 1000 (Ethernet)
RX packets 2157 bytes 2132896 (2.1 MB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 952 bytes 151610 (151.6 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
enp0s8: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.56.102 netmask 255.255.255.0 broadcast 192.168.56.255
inet6 fe80::20a:6c57:839d:2652 prefixlen 64 scopeid 0x20<link>
ether 08:00:27:53:45:82 txqueuelen 1000 (Ethernet)
RX packets 10597 bytes 1497146 (1.4 MB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 12058 bytes 1730219 (1.7 MB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 1000 (Local Loopback)
RX packets 1196 bytes 105396 (105.3 KB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 1196 bytes 105396 (105.3 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0Listing Network
Run the ls command to check all the networks running on the current host. You can see, seven networks are present currently including bridge, host and none which get created automatically when you install Docker. Depending on the containers I ran in the past, there are details of other custom networks also.
geekflare@geekflare:~$ docker network ls
NETWORK ID NAME DRIVER SCOPE
fec751a6ae21 bridge bridge local
21943b20735d docker_gwbridge bridge local
f51d1f3379e0 host host local
ppp8i7tvrxa0 ingress overlay swarm
ba68f73abeed mean-app_default bridge local
d466e75d86fa mean_default bridge local
5e5d9a192c00 none null localInspecting Network
You can run inspect command to get all the details about a network type. It gives information about the network which includes Name, Id, Created time, Scope, Driver, Config details such as Subnet and Gateway address. I will also give container details if any container is up and running. Otherwise, it will return an empty string.
geekflare@geekflare:~$ docker network inspect bridge
[
{
"Name": "bridge",
"Id": "fec751a6ae21f20a06cdc6eb823e773caec063b6bf9a388016594e59fd1db475",
"Created": "2019-08-01T10:30:27.595054009-04:00",
"Scope": "local",
"Driver": "bridge",
"EnableIPv6": false,
"IPAM": {
"Driver": "default",
"Options": null,
"Config": [
{
"Subnet": "172.17.0.0/16",
"Gateway": "172.17.0.1"
}
]
},
"Internal": false,
"Attachable": false,
"Ingress": false,
"ConfigFrom": {
"Network": ""
},
"ConfigOnly": false,
"Containers": {},
"Options": {
"com.docker.network.bridge.default_bridge": "true",
"com.docker.network.bridge.enable_icc": "true",
"com.docker.network.bridge.enable_ip_masquerade": "true",
"com.docker.network.bridge.host_binding_ipv4": "0.0.0.0",
"com.docker.network.bridge.name": "docker0",
"com.docker.network.driver.mtu": "1500"
},
"Labels": {}
}
]Create Network
Using create command, you can create your own you own network. You need to mention the driver type with --driver flag, in below example I am using bridge type.
geekflare@geekflare:~$ docker network create --driver bridge geekflare_network
08e0da91f6de6c640b1b6f8a8602973f310b8ee9b04961389b7dfda842ccc409Run the ls command to check if the network got created.
geekflare@geekflare:~$ docker network ls
NETWORK ID NAME DRIVER SCOPE
fec751a6ae21 bridge bridge local
21943b20735d docker_gwbridge bridge local
08e0da91f6de geekflare_network bridge local
f51d1f3379e0 host host local
ppp8i7tvrxa0 ingress overlay swarm
ba68f73abeed mean-app_default bridge local
d466e75d86fa mean_default bridge local
5e5d9a192c00 none null localNow I will run a docker container on the network I have created. I am running a simple apache server container in below command.
geekflare@geekflare:~$ docker run -it -d --network=geekflare_network httpd
38a0b0646da1a0045afcf7aa0cd6228b851f74107a6718bb19d599e896df1002Running inspect command to check all the information of geekflare_network. You can find the container details this time in this inspect the output; the container name is determined_dubinsky.
geekflare@geekflare:~$ docker network inspect geekflare_network
[
{
"Name": "geekflare_network",
"Id": "08e0da91f6de6c640b1b6f8a8602973f310b8ee9b04961389b7dfda842ccc409",
"Created": "2019-09-03T13:56:36.244295204-04:00",
"Scope": "local",
"Driver": "bridge",
"EnableIPv6": false,
"IPAM": {
"Driver": "default",
"Options": {},
"Config": [
{
"Subnet": "172.21.0.0/16",
"Gateway": "172.21.0.1"
}
]
},
"Internal": false,
"Attachable": false,
"Ingress": false,
"ConfigFrom": {
"Network": ""
},
"ConfigOnly": false,
"Containers": {
"38a0b0646da1a0045afcf7aa0cd6228b851f74107a6718bb19d599e896df1002": {
"Name": "determined_dubinsky",
"EndpointID": "30d252720e0f381ba01d6f5414525dff8587abcf3c4920100f112898a52c8a23",
"MacAddress": "02:42:ac:15:00:02",
"IPv4Address": "172.21.0.2/16",
"IPv6Address": ""
}
},
"Options": {},
"Labels": {}
}
]Disconnect Network
To disconnect the network from the container, run the command below. You need to mention the network name and the container name in disconnect command.
geekflare@geekflare:~$ docker network disconnect geekflare_network determined_dubinskyThis network won’t be running determined_dubinsky container anymore; the container field will be empty.
geekflare@geekflare:~$ docker network inspect geekflare_network
[
{
"Name": "geekflare_network",
"Id": "08e0da91f6de6c640b1b6f8a8602973f310b8ee9b04961389b7dfda842ccc409",
"Created": "2019-09-03T13:56:36.244295204-04:00",
"Scope": "local",
"Driver": "bridge",
"EnableIPv6": false,
"IPAM": {
"Driver": "default",
"Options": {},
"Config": [
{
"Subnet": "172.21.0.0/16",
"Gateway": "172.21.0.1"
}
]
},
"Internal": false,
"Attachable": false,
"Ingress": false,
"ConfigFrom": {
"Network": ""
},
"ConfigOnly": false,
"Containers": {},
"Options": {},
"Labels": {}
}
]To create other than bridge network, you need to mention the driver name other than bridge. To create an overlay network, run the command below.
geekflare@manager1:~$ docker network create --driver overlay geekflare_network_2
ynd2858eu1cngwhpc40m3h1nx
geekflare@manager1:~$ docker network ls
NETWORK ID NAME DRIVER SCOPE
fec751a6ae21 bridge bridge local
21943b20735d docker_gwbridge bridge local
08e0da91f6de geekflare_network bridge local
f51d1f3379e0 host host local
ppp8i7tvrxa0 ingress overlay swarm
ba68f73abeed mean-app_default bridge local
d466e75d86fa mean_default bridge local
5e5d9a192c00 none null local
ynd2858eu1cn geekflare_network_2 overlay swarmTo create a host network, mention host with –driver flag. The below example returns an error because only one host network instance is allowed, which was already running before. So, this command won’t create another host network.
geekflare@manager1:~$ docker network create --driver host geekflare_network_3
Error response from daemon: only one instance of "host" network is allowedConclusion
That was all about docker networking and how you can connect, disconnect, create, inspect docker networks. Try out these commands to get familiar with Docket networking. If you are curious in learning Net Devops then check out this Udemy course.
