I have a Docker container that needs to access a local REST API at http://127.0.0.1:8080. Using docker run --net=host works fine, but when I try to scale the container with Docker Compose, the container cannot reach the API. My Compose file uses:
version: "3"
services:
web:
image: containera:latest
network_mode: "host"
deploy:
replicas: 1
However, I get Ignoring unsupported options: network_mode. How can I configure docker compose network host properly to access the host network?
Hey! I’ve hit this exact issue 
. The key is that network_mode: "host" works only in single-host mode and is not supported with Docker Swarm’s deploy options, like replicas.
Example for a local Compose file:
version: "3.8"
services:
web:
image: containera:latest
network_mode: "host"
Do not include deploy.replicas if you want host networking.
On Linux, your container can now access 127.0.0.1:8080 on the host.
Works perfectly for development and local testing.
Why deploy.replicas breaks host networking
-
I ran into this myself and it was confusing. The reason:
-
deploy is a Swarm-only key, used for scaling services.
-
Swarm doesn’t support host networking for replicated services.
-
That’s why you see Ignoring unsupported options: network_mode.
My tip: If you want multiple replicas, you’ll need another networking strategy, not host mode.
If you need scaled containers that still reach the host API, you can’t rely on host networking. Instead:
Use the default bridge network.
Reference the host machine by its real IP (not 127.0.0.1):
version: "3.8"
services:
web:
image: containera:latest
networks:
- webnet
networks:
webnet:
driver: bridge
-
On Linux, the host IP can be 172.17.0.1 (Docker gateway) or your real LAN IP.
-
In the container: http://172.17.0.1:8080 instead of 127.0.0.1.
This approach works with scaling (replicas > 1) and avoids host network limitations