Search⌘ K
Home
Courses
Docker Deep Dive: Advanced Techniques

Test the Overlay Network

Explore testing Docker overlay network connectivity by identifying container IPs and names, and pinging between containers on different nodes. Understand how Docker facilitates secure, encrypted communication across hosts in a swarm setup, and trace network traffic to confirm direct container communication.

We'll cover the following...

The figure below shows the current setup with two containers running on different Docker hosts but connected to the same overlay.

Single overlay network spanning two Docker hosts on separate networks
Single overlay network spanning two Docker hosts on separate networks

The following steps will walk you through obtaining the container names and IP addresses and then seeing if they can ping each other.

The docker network inspect command

Switch back to node1 and run a docker network inspect to see the overlay network’s subnet information and any IP addresses it has assigned to service replicas.

$ docker network inspect uber-net
[
    {
        "Name": "uber-net",
        "Id": "vdu1yly429jvt04hgdm0mjqc6",
        "Scope": "swarm",
        "Driver": "overlay",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": null,
            "Config": [
                {
                    "Subnet": "10.0.0.0/24",                   <<---- Subnet info
                    "Gateway": "10.0.0.1"                      <<---- Subnet info
                }
        "Containers": {
                "Name": "test.1.tro80xqwm7k1bsyn3mt1fjkgk",    <<---- Replica ID
                "IPv4Address": "10.0.0.3/24",                  <<---- Container IP
                <Snip>
            },
<Snip>
Listing the details of the uber-net overlay network

We’ve snipped the output and highlighted the subnet information and the IPs ...