Docker "ingress" network cannot be configured as internal

Docker Engine Swarm
,
1

When I configure the Docker Swarm ingress network with --internal, the configuration is correctly applied. However, as soon as I create a service with a port published in ingress mode, Docker automatically switches Ingress from True to False.

Why Docker is refusing to have the ingress network be internal?

After creating the network:

[
    {
        "Name": "ingress",
        "Id": "yd5qtckhne6p4pxibziqhvy9y",
        "Created": "2025-06-06T12:48:16.694132526Z",
        "Scope": "swarm",
        "Driver": "overlay",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": null,
            "Config": [
                {
                    "Subnet": "172.20.0.0/24",
                    "Gateway": "172.20.0.1"
                }
            ]
        },
        "Internal": true,
        "Attachable": false,
        "Ingress": true,
        "ConfigFrom": {
            "Network": ""
        },
        "ConfigOnly": false,
        "Containers": null,
        "Options": {
            "com.docker.network.container_iface_prefix": "ingress",
            "com.docker.network.driver.overlay.vxlanid_list": "4103",
            "encrypted": ""
        },
        "Labels": null
    }
]

After creating a service with a port published in ingress mode:

[
    {
        "Name": "ingress",
        "Id": "yd5qtckhne6p4pxibziqhvy9y",
        "Created": "2025-06-06T12:48:30.695590187Z",
        "Scope": "swarm",
        "Driver": "overlay",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": null,
            "Config": [
                {
                    "Subnet": "172.20.0.0/24",
                    "Gateway": "172.20.0.1"
                }
            ]
        },
        "Internal": false,
        "Attachable": false,
        "Ingress": true,
        "ConfigFrom": {
            "Network": ""
        },
        "ConfigOnly": false,
        "Containers": {
            "ep-749e32b0fc027a85a3c4c5455c5145562424c29f939a46fa2fc8dae23a54a7d8": {
                "Name": "ingress-endpoint",
                "EndpointID": "749e32b0fc027a85a3c4c5455c5145562424c29f939a46fa2fc8dae23a54a7d8",
                "MacAddress": "02:42:ac:14:00:04",
                "IPv4Address": "172.20.0.4/24",
                "IPv6Address": ""
            }
        },
        "Options": {
            "com.docker.network.container_iface_prefix": "ingress",
            "com.docker.network.driver.overlay.vxlanid_list": "4103",
            "encrypted": ""
        },
        "Labels": {},
        "Peers": [
            {
                "Name": "8f138b3f965a",
                "IP": "192.168.82.13"
            },
            {
                "Name": "08b1511370b2",
                "IP": "192.168.82.11"
            },
            {
                "Name": "c56f0eee981c",
                "IP": "192.168.82.12"
            }
        ]
    }
]

For context, the reason I’m trying to configure the ingress network as internal is to prevent internet access for my service.

2

I wrote about internal network shere:

In short, you cannot have port forwards on an internal network. It is only for internal communication between containers. You can add a second network for ingress if you want.

3

Okay, so if I want to publish a port in ingress mode, the container must be attached to a bridge network at some point. This means I can’t prevent internet access to the container exposing ports, as without a bridge it can’t accept incoming connections.
Am I correct?

4

I have an example in the article in which I use an internal network and an additional proxy that has the internal network and another for incomming requests. It is compose, not Swarm, but I expect it to be the same in Swarm. That way you can isolate pods and alllow incomming requests only through the proxy container that has access to the isolated pods.

5

Okay, I though the swarm routing mesh was working like the proxy in your example. Therefore, I couldn’t understand why I couldn’t have the ingress handle the incoming connections and forward them to my container, while the container is only linked to the ingress network. But in fact it’s not a proxy, but more like a port forward that listen on all nodes.