Docker网络原理及自定义网络详细解析

Docker在宿主机上虚拟了一个网桥，当创建并启动容器的时候，每一个容器默认都会被分配一个跟网桥网段一致的ip，网桥作为容器的网关，网桥与每一个容器联通，容器间通过网桥可以通信。由于网桥是虚拟出来的，外网无法进行寻址，也就是默认外网无法访问容器，需要在创建启动容器时把宿主机的端口与容器端口进行映射，通过宿主机IP端口访问容器。这是Docker默认的网络，它有一个弊端是只能通过IP让容器互相访问，如果想使用容器名称或容器ID互相访问需要在创建启动容器时候用link的方式修改hosts文件实现。一般使用自定义网络，自定义网络使用network创建，创建时可以指定子网网段及网关等信息，在创建并启动容器时指定使用的网络。这样在一个自定义网络里的所有容器可以直接使用容器名进行访问，如果一个容器想要访问其他网络中的容器也可以在network中进行设置，这样这个容器与目标网络的容器可以使用容器名通信。

1 默认网络docker0

用vm虚拟机测试，未启动docker 系统中有两个网络（回环网络、虚拟机网络）

当启动docker服务后，宿主机多出一个网络docker0 这就是docker默认网络

# 启动docker服务
[root@localhost ~]# systemctl start docker

启动一个tomcat容器，会发现宿主机又多出一个网络

启动tomcat
[root@localhost ~]# docker run -d -P --name tomcat1 tomcat

再启动一个tomcat，会发展宿主机又多出一个网络

# 启动tomcat
[root@localhost ~]# docker run -d -P --name tomcat2 tomcat

测试两个tomcat网络ip是通的

# 查看tomcat的ip地址
[root@localhost ~]# docker exec -it tomcat2 ip addr
1: lo:  mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
9: eth0@if10:  mtu 1500 qdisc noqueue state UP group default
    link/ether 02:42:ac:11:00:03 brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet 172.17.0.3/16 brd 172.17.255.255 scope global eth0
valid_lft forever preferred_lft forever
# 在tomcat1 ping tomcat2的ip
[root@localhost ~]# docker exec -it tomcat1 ping 172.17.0.3
PING 172.17.0.3 (172.17.0.3) 56(84) bytes of data.
64 bytes from 172.17.0.3: icmp_seq=1 ttl=64 time=0.146 ms
64 bytes from 172.17.0.3: icmp_seq=2 ttl=64 time=0.067 ms
64 bytes from 172.17.0.3: icmp_seq=3 ttl=64 time=0.088 ms
^C
--- 172.17.0.3 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 5ms
rtt min/avg/max/mdev = 0.067/0.100/0.146/0.034 ms

在tomcat1里ping tomcat2的容器名无法ping通

# 在tomcat1里ping tomcat2的容器名
[root@localhost ~]# docker exec -it tomcat1 ping tomcat2
^C[root@localhost ~]#

停止tomcat1 重新创建启动tomcat 使用link 会在底层修改tomcat1 的hosts文件实现容器名作为ip域名从而tomcat1到tomcat2的单向ping通

# 删除tomcat1
[root@localhost ~]# docker rm -f tomcat1
tomcat1
 
# 查看run的帮助文档 link用法
[root@localhost ~]# docker run --help
 
Usage:  docker run [OPTIONS] IMAGE [COMMAND] [ARG...]
 
Run a command in a new container
 
Options:
      --add-host list    Add a custom host-to-IP mapping (host:ip)
  -a, --attach list      Attach to STDIN, STDOUT or STDERR
      --blkio-weight uint16     Block IO (relative weight), between 10 and 1000, or 0 to disable (default 0)
      --blkio-weight-device listBlock IO weight (relative device weight) (default [])
      --cap-add list     Add Linux capabilities
      --cap-drop list    Drop Linux capabilities
      --cgroup-parent string    Optional parent cgroup for the container
      --cgroupns string  Cgroup namespace to use (host|private)
    'host':    Run the container in the Docker host's cgroup namespace
    'private': Run the container in its own private cgroup namespace
    '': Use the cgroup namespace as configured by the
 default-cgroupns-mode option on the daemon (default)
      --cidfile string   Write the container ID to the file
      --cpu-period int   Limit CPU CFS (Completely Fair Scheduler) period
      --cpu-quota int    Limit CPU CFS (Completely Fair Scheduler) quota
      --cpu-rt-period intLimit CPU real-time period in microseconds
      --cpu-rt-runtime int      Limit CPU real-time runtime in microseconds
  -c, --cpu-shares int   CPU shares (relative weight)
      --cpus decimal     Number of CPUs
      --cpuset-cpus string      CPUs in which to allow execution (0-3, 0,1)
      --cpuset-mems string      MEMs in which to allow execution (0-3, 0,1)
  -d, --detach    Run container in background and print container ID
      --detach-keys string      Override the key sequence for detaching a container
      --device list      Add a host device to the container
      --device-cgroup-rule list Add a rule to the cgroup allowed devices list
      --device-read-bps list    Limit read rate (bytes per second) from a device (default [])
      --device-read-iops list   Limit read rate (IO per second) from a device (default [])
      --device-write-bps list   Limit write rate (bytes per second) to a device (default [])
      --device-write-iops list  Limit write rate (IO per second) to a device (default [])
      --disable-content-trust   Skip image verification (default true)
      --dns list  Set custom DNS servers
      --dns-option list  Set DNS options
      --dns-search list  Set custom DNS search domains
      --domainname stringContainer NIS domain name
      --entrypoint stringOverwrite the default ENTRYPOINT of the image
  -e, --env list  Set environment variables
      --env-file list    Read in a file of environment variables
      --expose list      Expose a port or a range of ports
      --gpus gpu-request GPU devices to add to the container ('all' to pass all GPUs)
      --group-add list   Add additional groups to join
      --health-cmd stringCommand to run to check health
      --health-interval durationTime between running the check (ms|s|m|h) (default 0s)
      --health-retries int      Consecutive failures needed to report unhealthy
      --health-start-period duration   Start period for the container to initialize before starting health-retries countdown
    (ms|s|m|h) (default 0s)
      --health-timeout duration Maximum time to allow one check to run (ms|s|m|h) (default 0s)
      --help      Print usage
  -h, --hostname string  Container host name
      --init      Run an init inside the container that forwards signals and reaps processes
  -i, --interactive      Keep STDIN open even if not attached
      --ip string IPv4 address (e.g., 172.30.100.104)
      --ip6 stringIPv6 address (e.g., 2001:db8::33)
      --ipc stringIPC mode to use
      --isolation string Container isolation technology
      --kernel-memory bytes     Kernel memory limit
  -l, --label listSet meta data on a container
      --label-file list  Read in a line delimited file of labels
      --link list Add link to another container
      --link-local-ip list      Container IPv4/IPv6 link-local addresses
      --log-driver stringLogging driver for the container
      --log-opt list     Log driver options
      --mac-address string      Container MAC address (e.g., 92:d0:c6:0a:29:33)
  -m, --memory bytes     Memory limit
      --memory-reservation bytesMemory soft limit
      --memory-swap bytesSwap limit equal to memory plus swap: '-1' to enable unlimited swap
      --memory-swappiness int   Tune container memory swappiness (0 to 100) (default -1)
      --mount mount      Attach a filesystem mount to the container
      --name string      Assign a name to the container
      --network network  Connect a container to a network
      --network-alias list      Add network-scoped alias for the container
      --no-healthcheck   Disable any container-specified HEALTHCHECK
      --oom-kill-disable Disable OOM Killer
      --oom-score-adj intTune host's OOM preferences (-1000 to 1000)
      --pid stringPID namespace to use
      --pids-limit int   Tune container pids limit (set -1 for unlimited)
      --platform string  Set platform if server is multi-platform capable
      --privilegedGive extended privileges to this container
  -p, --publish list     Publish a container's port(s) to the host
  -P, --publish-all      Publish all exposed ports to random ports
      --pull string      Pull image before running ("always"|"missing"|"never") (default "missing")
      --read-only Mount the container's root filesystem as read only
      --restart string   Restart policy to apply when a container exits (default "no")
      --rm Automatically remove the container when it exits
      --runtime string   Runtime to use for this container
      --security-opt listSecurity Options
      --shm-size bytes   Size of /dev/shm
      --sig-proxy Proxy received signals to the process (default true)
      --stop-signal string      Signal to stop a container (default "SIGTERM")
      --stop-timeout int Timeout (in seconds) to stop a container
      --storage-opt list Storage driver options for the container
      --sysctl mapSysctl options (default map[])
      --tmpfs listMount a tmpfs directory
  -t, --ttyAllocate a pseudo-TTY
      --ulimit ulimit    Ulimit options (default [])
  -u, --user string      Username or UID (format: [:])
      --userns string    User namespace to use
      --uts stringUTS namespace to use
  -v, --volume list      Bind mount a volume
      --volume-driver string    Optional volume driver for the container
      --volumes-from listMount volumes from the specified container(s)
  -w, --workdir string   Working directory inside the container
 
# 启动tomcat1 link指定要访问的容器名
[root@localhost ~]# docker run -d -P --name tomcat1 --link tomcat2 tomcat
f78c51961662a1d3558fc8d0d95906b902a7a042f251a60858e72bcfa62e7a08
 
# 测试ping
[root@localhost ~]# docker exec -it tomcat1 ping tomcat2
PING tomcat2 (172.17.0.3) 56(84) bytes of data.
64 bytes from tomcat2 (172.17.0.3): icmp_seq=1 ttl=64 time=0.088 ms
64 bytes from tomcat2 (172.17.0.3): icmp_seq=2 ttl=64 time=0.071 ms
64 bytes from tomcat2 (172.17.0.3): icmp_seq=3 ttl=64 time=0.071 ms
^C
--- tomcat2 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 1000ms
rtt min/avg/max/mdev = 0.071/0.076/0.088/0.012 ms
 
# 查看tomcat1的hosts已经加入了tomcat2的域名
[root@localhost ~]# docker exec -it tomcat1 cat /etc/hosts
127.0.0.1localhost
::1     localhost ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
172.17.0.3      tomcat2 27766c324de6
172.17.0.2      f78c51961662
 
# tomcat2无法ping通tomcat1
[root@localhost ~]# docker exec -it tomcat2 ping tomcat1
^C[root@localhost ~]#

2 自定义网络

需要用到network命令

# 查看帮助文档
[root@localhost ~]# docker network --help
 
Usage:  docker network COMMAND
 
Manage networks
 
Commands:
  connect     Connect a container to a network
  create      Create a network
  disconnect  Disconnect a container from a network
  inspect     Display detailed information on one or more networks
  ls   List networks
  pruneRemove all unused networks
  rm   Remove one or more networks
 
Run 'docker network COMMAND --help' for more information on a command.

列出当前的docker网络 bridge为默认网络docker0

[root@localhost ~]# docker network ls
NETWORK ID     NAME      DRIVER    SCOPE
9b27ff0926bf   bridge    bridge    local
8dfa2efae677   host      host      local
2025b7fb1d7c   none      null      local

创建网络mynet

[root@localhost ~]# docker network create --help
 
Usage:  docker network create [OPTIONS] NETWORK
 
Create a network
 
Options:
      --attachable    Enable manual container attachment
      --aux-address map      Auxiliary IPv4 or IPv6 addresses used by Network driver (default map[])
      --config-from string   The network from which to copy the configuration
      --config-only   Create a configuration only network
  -d, --driver string Driver to manage the Network (default "bridge")
      --gateway strings      IPv4 or IPv6 Gateway for the master subnet
      --ingressCreate swarm routing-mesh network
      --internal      Restrict external access to the network
      --ip-range strings     Allocate container ip from a sub-range
      --ipam-driver string   IP Address Management Driver (default "default")
      --ipam-opt map  Set IPAM driver specific options (default map[])
      --ipv6   Enable IPv6 networking
      --label list    Set metadata on a network
  -o, --opt mapSet driver specific options (default map[])
      --scope string  Control the network's scope
      --subnet stringsSubnet in CIDR format that represents a network segment
[root@localhost ~]# docker network create --driver bridge --subnet 192.168.0.0/16 --gateway 192.168.0.1 mynet
1abaa8e6a387bc8bbc7ac50d9f2289e96a143a92f074e90f698bd70411c86672
[root@localhost ~]# docker network inspect mynet
[
    {
 "Name": "mynet",
 "Id": "1abaa8e6a387bc8bbc7ac50d9f2289e96a143a92f074e90f698bd70411c86672",
 "Created": "2021-05-13T11:21:13.494039122+08:00",
 "Scope": "local",
 "Driver": "bridge",
 "EnableIPv6": false,
 "IPAM": {
     "Driver": "default",
     "Options": {},
     "Config": [
  {
      "Subnet": "192.168.0.0/16",
      "Gateway": "192.168.0.1"
  }
     ]
 },
 "Internal": false,
 "Attachable": false,
 "Ingress": false,
 "ConfigFrom": {
     "Network": ""
 },
 "ConfigOnly": false,
 "Containers": {},
 "Options": {},
 "Labels": {}
    }
]

使用mynet创建启动两个tomcat,他们可以直接通过容器名称双向互相ping通

[root@localhost ~]# docker run --help
 
Usage:  docker run [OPTIONS] IMAGE [COMMAND] [ARG...]
 
Run a command in a new container
 
Options:
      --add-host list    Add a custom host-to-IP mapping (host:ip)
  -a, --attach list      Attach to STDIN, STDOUT or STDERR
      --blkio-weight uint16     Block IO (relative weight), between 10 and 1000, or 0 to disable (default 0)
      --blkio-weight-device listBlock IO weight (relative device weight) (default [])
      --cap-add list     Add Linux capabilities
      --cap-drop list    Drop Linux capabilities
      --cgroup-parent string    Optional parent cgroup for the container
      --cgroupns string  Cgroup namespace to use (host|private)
    'host':    Run the container in the Docker host's cgroup namespace
    'private': Run the container in its own private cgroup namespace
    '': Use the cgroup namespace as configured by the
 default-cgroupns-mode option on the daemon (default)
      --cidfile string   Write the container ID to the file
      --cpu-period int   Limit CPU CFS (Completely Fair Scheduler) period
      --cpu-quota int    Limit CPU CFS (Completely Fair Scheduler) quota
      --cpu-rt-period intLimit CPU real-time period in microseconds
      --cpu-rt-runtime int      Limit CPU real-time runtime in microseconds
  -c, --cpu-shares int   CPU shares (relative weight)
      --cpus decimal     Number of CPUs
      --cpuset-cpus string      CPUs in which to allow execution (0-3, 0,1)
      --cpuset-mems string      MEMs in which to allow execution (0-3, 0,1)
  -d, --detach    Run container in background and print container ID
      --detach-keys string      Override the key sequence for detaching a container
      --device list      Add a host device to the container
      --device-cgroup-rule list Add a rule to the cgroup allowed devices list
      --device-read-bps list    Limit read rate (bytes per second) from a device (default [])
      --device-read-iops list   Limit read rate (IO per second) from a device (default [])
      --device-write-bps list   Limit write rate (bytes per second) to a device (default [])
      --device-write-iops list  Limit write rate (IO per second) to a device (default [])
      --disable-content-trust   Skip image verification (default true)
      --dns list  Set custom DNS servers
      --dns-option list  Set DNS options
      --dns-search list  Set custom DNS search domains
      --domainname stringContainer NIS domain name
      --entrypoint stringOverwrite the default ENTRYPOINT of the image
  -e, --env list  Set environment variables
      --env-file list    Read in a file of environment variables
      --expose list      Expose a port or a range of ports
      --gpus gpu-request GPU devices to add to the container ('all' to pass all GPUs)
      --group-add list   Add additional groups to join
      --health-cmd stringCommand to run to check health
      --health-interval durationTime between running the check (ms|s|m|h) (default 0s)
      --health-retries int      Consecutive failures needed to report unhealthy
      --health-start-period duration   Start period for the container to initialize before starting health-retries countdown
    (ms|s|m|h) (default 0s)
      --health-timeout duration Maximum time to allow one check to run (ms|s|m|h) (default 0s)
      --help      Print usage
  -h, --hostname string  Container host name
      --init      Run an init inside the container that forwards signals and reaps processes
  -i, --interactive      Keep STDIN open even if not attached
      --ip string IPv4 address (e.g., 172.30.100.104)
      --ip6 stringIPv6 address (e.g., 2001:db8::33)
      --ipc stringIPC mode to use
      --isolation string Container isolation technology
      --kernel-memory bytes     Kernel memory limit
  -l, --label listSet meta data on a container
      --label-file list  Read in a line delimited file of labels
      --link list Add link to another container
      --link-local-ip list      Container IPv4/IPv6 link-local addresses
      --log-driver stringLogging driver for the container
      --log-opt list     Log driver options
      --mac-address string      Container MAC address (e.g., 92:d0:c6:0a:29:33)
  -m, --memory bytes     Memory limit
      --memory-reservation bytesMemory soft limit
      --memory-swap bytesSwap limit equal to memory plus swap: '-1' to enable unlimited swap
      --memory-swappiness int   Tune container memory swappiness (0 to 100) (default -1)
      --mount mount      Attach a filesystem mount to the container
      --name string      Assign a name to the container
      --network network  Connect a container to a network
      --network-alias list      Add network-scoped alias for the container
      --no-healthcheck   Disable any container-specified HEALTHCHECK
      --oom-kill-disable Disable OOM Killer
      --oom-score-adj intTune host's OOM preferences (-1000 to 1000)
      --pid stringPID namespace to use
      --pids-limit int   Tune container pids limit (set -1 for unlimited)
      --platform string  Set platform if server is multi-platform capable
      --privilegedGive extended privileges to this container
  -p, --publish list     Publish a container's port(s) to the host
  -P, --publish-all      Publish all exposed ports to random ports
      --pull string      Pull image before running ("always"|"missing"|"never") (default "missing")
      --read-only Mount the container's root filesystem as read only
      --restart string   Restart policy to apply when a container exits (default "no")
      --rm Automatically remove the container when it exits
      --runtime string   Runtime to use for this container
      --security-opt listSecurity Options
      --shm-size bytes   Size of /dev/shm
      --sig-proxy Proxy received signals to the process (default true)
      --stop-signal string      Signal to stop a container (default "SIGTERM")
      --stop-timeout int Timeout (in seconds) to stop a container
      --storage-opt list Storage driver options for the container
      --sysctl mapSysctl options (default map[])
      --tmpfs listMount a tmpfs directory
  -t, --ttyAllocate a pseudo-TTY
      --ulimit ulimit    Ulimit options (default [])
  -u, --user string      Username or UID (format: [:])
      --userns string    User namespace to use
      --uts stringUTS namespace to use
  -v, --volume list      Bind mount a volume
      --volume-driver string    Optional volume driver for the container
      --volumes-from listMount volumes from the specified container(s)
  -w, --workdir string   Working directory inside the container
[root@localhost ~]# docker run -d -P --name tomcat-n-1 --network mynet tomcat
404e4e63622b207af2ed534e768996f4d1cba4c798bba9e5d9b33c42711eaa4a
[root@localhost ~]# docker run -d -P --name tomcat-n-2 --network mynet tomcat
f6352fb3db01beed6ddf17ef84999a4ab209f026a6137b3bc7e35335d434785f
[root@localhost ~]# docker ps
ConTAINER ID   IMAGE     COMMAND      CREATED   STATUS   PORTS      NAMES
f6352fb3db01   tomcat    "catalina.sh run"   3 seconds ago    Up 2 seconds    0.0.0.0:49159->8080/tcp, :::49159->8080/tcp   tomcat-n-2
404e4e63622b   tomcat    "catalina.sh run"   10 seconds ago   Up 9 seconds    0.0.0.0:49158->8080/tcp, :::49158->8080/tcp   tomcat-n-1
f78c51961662   tomcat    "catalina.sh run"   15 minutes ago   Up 15 minutes   0.0.0.0:49157->8080/tcp, :::49157->8080/tcp   tomcat1
27766c324de6   tomcat    "catalina.sh run"   16 minutes ago   Up 16 minutes   0.0.0.0:49156->8080/tcp, :::49156->8080/tcp   tomcat2
[root@localhost ~]# docker exec -it tomcat-n-1 ping tomcat-n-2
PING tomcat-n-2 (192.168.0.3) 56(84) bytes of data.
64 bytes from tomcat-n-2.mynet (192.168.0.3): icmp_seq=1 ttl=64 time=0.102 ms
64 bytes from tomcat-n-2.mynet (192.168.0.3): icmp_seq=2 ttl=64 time=0.069 ms
64 bytes from tomcat-n-2.mynet (192.168.0.3): icmp_seq=3 ttl=64 time=0.164 ms
^C
--- tomcat-n-2 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 3ms
rtt min/avg/max/mdev = 0.069/0.111/0.164/0.041 ms

查看mynet网络的详细信息，包含了启动的两个tomcat容器的网络信息

[root@localhost ~]# docker network inspect mynet
[
    {
 "Name": "mynet",
 "Id": "1abaa8e6a387bc8bbc7ac50d9f2289e96a143a92f074e90f698bd70411c86672",
 "Created": "2021-05-13T11:21:13.494039122+08:00",
 "Scope": "local",
 "Driver": "bridge",
 "EnableIPv6": false,
 "IPAM": {
     "Driver": "default",
     "Options": {},
     "Config": [
  {
      "Subnet": "192.168.0.0/16",
      "Gateway": "192.168.0.1"
  }
     ]
 },
 "Internal": false,
 "Attachable": false,
 "Ingress": false,
 "ConfigFrom": {
     "Network": ""
 },
 "ConfigOnly": false,
 "Containers": {
     "404e4e63622b207af2ed534e768996f4d1cba4c798bba9e5d9b33c42711eaa4a": {
  "Name": "tomcat-n-1",
  "EndpointID": "b9efbd78daabe9345ade2a2e55291b7646d01679516e2f0be1efd5c2d6fea6b8",
  "MacAddress": "02:42:c0:a8:00:02",
  "IPv4Address": "192.168.0.2/16",
  "IPv6Address": ""
     },
     "f6352fb3db01beed6ddf17ef84999a4ab209f026a6137b3bc7e35335d434785f": {
  "Name": "tomcat-n-2",
  "EndpointID": "6b05a1ceff43514305bf3d0adf9e30ba8007db5ec8349d47f96ff2b216912fc0",
  "MacAddress": "02:42:c0:a8:00:03",
  "IPv4Address": "192.168.0.3/16",
  "IPv6Address": ""
     }
 },
 "Options": {},
 "Labels": {}
    }
]

启动一个tomcat3使用默认网络docker0

[root@localhost ~]# docker run -d -P --name tomcat3 tomcat
90e94ac30a3c61b493d2ea38c32cf5dddb781e88c30547b609db765b15d7d1e0
[root@localhost ~]# docker network ls
NETWORK ID     NAME      DRIVER    SCOPE
9b27ff0926bf   bridge    bridge    local
8dfa2efae677   host      host      local
1abaa8e6a387   mynet     bridge    local
2025b7fb1d7c   none      null      local
 
# 查看docker0详细信息 tomcat3出现在默认网络里
[root@localhost ~]# docker network inspect 9b27ff0926bf
[
    {
 "Name": "bridge",
 "Id": "9b27ff0926bf22d0828ccd07d6e14eb17d96a4989f9def6f9118c099cf1ca1c6",
 "Created": "2021-05-13T10:51:20.244232273+08:00",
 "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": {
     "27766c324de619b24e2ed522d8064c5a4610c8f509ff0aed8fa1719691f01bf1": {
  "Name": "tomcat2",
  "EndpointID": "de913778ce2d7478e25daca26809aa75c9093c43853d9420c70886fb16741722",
  "MacAddress": "02:42:ac:11:00:03",
  "IPv4Address": "172.17.0.3/16",
  "IPv6Address": ""
     },
     "90e94ac30a3c61b493d2ea38c32cf5dddb781e88c30547b609db765b15d7d1e0": {
  "Name": "tomcat3",
  "EndpointID": "2223e522a0950b846bb7691b31f60bbd88ab3c9b8e71d601a495cce39387b8cc",
  "MacAddress": "02:42:ac:11:00:04",
  "IPv4Address": "172.17.0.4/16",
  "IPv6Address": ""
     },
     "f78c51961662a1d3558fc8d0d95906b902a7a042f251a60858e72bcfa62e7a08": {
  "Name": "tomcat1",
  "EndpointID": "59299fdca5497e55dc5a94e408529cc98819b673568720c81aa1c554dff1bbe5",
  "MacAddress": "02:42:ac:11:00:02",
  "IPv4Address": "172.17.0.2/16",
  "IPv6Address": ""
     }
 },
 "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": {}
    }
]

tomcat3和mynet不在一个网络，tomcat3无法访问mynet网络里的两个tomcat，可以使用network打通tomcat3和mynetwork，实现双向互相访问（支持容器名称）。

# 查看mynet网络里容器的ip
[root@localhost ~]# docker network inspect mynet
[
    {
 "Name": "mynet",
 "Id": "1abaa8e6a387bc8bbc7ac50d9f2289e96a143a92f074e90f698bd70411c86672",
 "Created": "2021-05-13T11:21:13.494039122+08:00",
 "Scope": "local",
 "Driver": "bridge",
 "EnableIPv6": false,
 "IPAM": {
     "Driver": "default",
     "Options": {},
     "Config": [
  {
      "Subnet": "192.168.0.0/16",
      "Gateway": "192.168.0.1"
  }
     ]
 },
 "Internal": false,
 "Attachable": false,
 "Ingress": false,
 "ConfigFrom": {
     "Network": ""
 },
 "ConfigOnly": false,
 "Containers": {
     "404e4e63622b207af2ed534e768996f4d1cba4c798bba9e5d9b33c42711eaa4a": {
  "Name": "tomcat-n-1",
  "EndpointID": "b9efbd78daabe9345ade2a2e55291b7646d01679516e2f0be1efd5c2d6fea6b8",
  "MacAddress": "02:42:c0:a8:00:02",
  "IPv4Address": "192.168.0.2/16",
  "IPv6Address": ""
     },
     "f6352fb3db01beed6ddf17ef84999a4ab209f026a6137b3bc7e35335d434785f": {
  "Name": "tomcat-n-2",
  "EndpointID": "6b05a1ceff43514305bf3d0adf9e30ba8007db5ec8349d47f96ff2b216912fc0",
  "MacAddress": "02:42:c0:a8:00:03",
  "IPv4Address": "192.168.0.3/16",
  "IPv6Address": ""
     }
 },
 "Options": {},
 "Labels": {}
    }
]
 
# tomcat3 ping ip不通
[root@localhost ~]# docker exec -it tomcat3 ping 192.168.0.2
PING 192.168.0.2 (192.168.0.2) 56(84) bytes of data.
^C
--- 192.168.0.2 ping statistics ---
7 packets transmitted, 0 received, 100% packet loss, time 11ms
 
[root@localhost ~]# docker exec -it tomcat3 ping 192.168.0.3
PING 192.168.0.3 (192.168.0.3) 56(84) bytes of data.
^C
--- 192.168.0.3 ping statistics ---
9 packets transmitted, 0 received, 100% packet loss, time 20ms

# 使用connect联通一个网络和另外一个网络里的容器，可以互相容器名称访问
[root@localhost ~]# docker network connect --help
 
Usage:  docker network connect [OPTIONS] NETWORK ConTAINER
 
Connect a container to a network
 
Options:
      --alias strings    Add network-scoped alias for the container
      --driver-opt strings      driver options for the network
      --ip string IPv4 address (e.g., 172.30.100.104)
      --ip6 stringIPv6 address (e.g., 2001:db8::33)
      --link list Add link to another container
      --link-local-ip strings   Add a link-local address for the container
[root@localhost ~]# docker network connect mynet tomcat3
[root@localhost ~]# docker exec -it tomcat3 ping tomcat-n-1
PING tomcat-n-1 (192.168.0.2) 56(84) bytes of data.
64 bytes from tomcat-n-1.mynet (192.168.0.2): icmp_seq=1 ttl=64 time=0.235 ms
64 bytes from tomcat-n-1.mynet (192.168.0.2): icmp_seq=2 ttl=64 time=0.070 ms
64 bytes from tomcat-n-1.mynet (192.168.0.2): icmp_seq=3 ttl=64 time=0.064 ms
^C
--- tomcat-n-1 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 6ms
rtt min/avg/max/mdev = 0.064/0.123/0.235/0.079 ms
[root@localhost ~]# docker exec -it tomcat-n-1 ping tomcat3
PING tomcat3 (192.168.0.4) 56(84) bytes of data.
64 bytes from tomcat3.mynet (192.168.0.4): icmp_seq=1 ttl=64 time=0.055 ms
64 bytes from tomcat3.mynet (192.168.0.4): icmp_seq=2 ttl=64 time=0.169 ms
64 bytes from tomcat3.mynet (192.168.0.4): icmp_seq=3 ttl=64 time=0.194 ms
^C
--- tomcat3 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 6ms
rtt min/avg/max/mdev = 0.055/0.139/0.194/0.061 ms

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