Modify docker's default network card (bridge)

The default network card of the docker engine is docker0. When systemctl start docker starts the container server, a network card device with a network segment of 172.17.10.1/24 will be generated by default.
docker0 is not only a virtual network card, but also a virtual switch
Network card: realizes its communication with the host
virtual switch: Add its gateway to the container, so that the container can communicate with the container, and the container and the external network

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The eth0 at the bottom of the figure is the external network card device of this machine

How to add a custom network card?

1. Obtain the local network card ifconfig
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2. Manually create a virtual network card (bridge)
cd /etc/sysconfig/network-scripts
cp ifcfg-ens33 ifcfg-br0
[root@node2 network-scripts]# vi ifcfg-br0
TYPE= "Bridge"
Bridge = "BR0"
Bootproto = Static
Defroute = YES
NAME = BR0
Device = BR0
Onbook = YES
iPaddr = 192.168.10.135
Gateway = 192.168.10.2
Netmask = 255.255.255.0
DNS1 = 8.8.8.8
3. Start new network card ( Bridge) ifconfig br0 up
4. Modify the docker.service file and add the parameter of -b br0
[root@node2 network-scripts]# vi /usr/lib/systemd/system/docker.service

ExecStart=/usr/bin/dockerd-current -b br0
specifies that the network card when starting the service is br0
5. Make the parameters take effect:
systemctl daemon-reload
systemctl restart docker
6. Check the network, and br0 takes effect:

[root@node2 ~]# ifconfig
br0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 172.18.0.1  netmask 255.255.0.0  broadcast 0.0.0.0
        ether 76:3e:f8:46:5e:e1  txqueuelen 1000  (Ethernet)
        RX packets 16  bytes 1088 (1.0 KiB)
        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

docker0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        inet 172.17.10.1  netmask 255.255.255.0  broadcast 0.0.0.0
        inet6 fe80::42:4aff:fe6b:8061  prefixlen 64  scopeid 0x20<link>
        ether 02:42:4a:6b:80:61  txqueuelen 0  (Ethernet)
        RX packets 24  bytes 1632 (1.5 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 8  bytes 656 (656.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.10.135  netmask 255.255.255.0  broadcast 192.168.10.255
        inet6 fe80::9b50:e592:a2e1:5127  prefixlen 64  scopeid 0x20<link>
        ether 00:50:56:26:02:e6  txqueuelen 1000  (Ethernet)
        RX packets 862  bytes 69807 (68.1 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0

6. Start a new container

[root@node2 ~]# docker run -itd --name=nginx4 192.168.10.135:5000/nginx:v1
8bb095b460888d2519101bdcb7b47a617a55682b6d97ab4529c1cdbf8d458532

Check that the IP of the container is the network segment of the br0 network card:

[root@node2 docker-static-ip]# docker inspect nginx4|grep -i ipa
            "SecondaryIPAddresses": null,
            "IPAddress": "172.18.0.3"

Modify docker's default network card (bridge)

How to add a custom network card?

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