Near the top, information about the `bridge` network is listed, including
    the IP address of the gateway between the Docker host and the `bridge`
    network (`172.17.0.1`). Under the `Containers` key, each connected container
    is listed, along with information about its IP address (`172.17.0.2` for
    `alpine1` and `172.17.0.3` for `alpine2`).

4.  The containers are running in the background. Use the `docker attach`
    command to connect to `alpine1`.

    ```console
    $ docker attach alpine1

    / #
    ```

    The prompt changes to `#` to indicate that you are the `root` user within
    the container. Use the `ip addr show` command to show the network interfaces
    for `alpine1` as they look from within the container:

    ```console
    # ip addr show

    1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1
        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
        inet6 ::1/128 scope host
           valid_lft forever preferred_lft forever
    27: eth0@if28: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1500 qdisc noqueue state UP
        link/ether 02:42:ac:11:00:02 brd ff:ff:ff:ff:ff:ff
        inet 172.17.0.2/16 scope global eth0
           valid_lft forever preferred_lft forever
        inet6 fe80::42:acff:fe11:2/64 scope link
           valid_lft forever preferred_lft forever
    ```

    The first interface is the loopback device. Ignore it for now. Notice that
    the second interface has the IP address `172.17.0.2`, which is the same
    address shown for `alpine1` in the previous step.

5.  From within `alpine1`, make sure you can connect to the internet by
    pinging `google.com`. The `-c 2` flag limits the command to two `ping`
    attempts.

    ```console
    # ping -c 2 google.com

    PING google.com (172.217.3.174): 56 data bytes
    64 bytes from 172.217.3.174: seq=0 ttl=41 time=9.841 ms
    64 bytes from 172.217.3.174: seq=1 ttl=41 time=9.897 ms

    --- google.com ping statistics ---
    2 packets transmitted, 2 packets received, 0% packet loss
    round-trip min/avg/max = 9.841/9.869/9.897 ms
    ```

6.  Now try to ping the second container. First, ping it by its IP address,
    `172.17.0.3`:

    ```console
    # ping -c 2 172.17.0.3

    PING 172.17.0.3 (172.17.0.3): 56 data bytes
    64 bytes from 172.17.0.3: seq=0 ttl=64 time=0.086 ms
    64 bytes from 172.17.0.3: seq=1 ttl=64 time=0.094 ms

    --- 172.17.0.3 ping statistics ---
    2 packets transmitted, 2 packets received, 0% packet loss
    round-trip min/avg/max = 0.086/0.090/0.094 ms
    ```

    This succeeds. Next, try pinging the `alpine2` container by container
    name. This will fail.

    ```console
    # ping -c 2 alpine2

    ping: bad address 'alpine2'
    ```

7.  Detach from `alpine1` without stopping it by using the detach sequence,
    `CTRL` + `p` `CTRL` + `q` (hold down `CTRL` and type `p` followed by `q`).
    If you wish, attach to `alpine2` and repeat steps 4, 5, and 6 there,
    substituting `alpine1` for `alpine2`.

8.  Stop and remove both containers.

    ```console
    $ docker container stop alpine1 alpine2
    $ docker container rm alpine1 alpine2
    ```

Remember, the default `bridge` network is not recommended for production. To
learn about user-defined bridge networks, continue to the
[next tutorial](#use-user-defined-bridge-networks).

## Use user-defined bridge networks

In this example, we again start two `alpine` containers, but attach them to a
user-defined network called `alpine-net` which we have already created. These
containers are not connected to the default `bridge` network at all. We then
start a third `alpine` container which is connected to the `bridge` network but
not connected to `alpine-net`, and a fourth `alpine` container which is
connected to both networks.

1.  Create the `alpine-net` network. You do not need the `--driver bridge` flag
    since it's the default, but this example shows how to specify it.