Description

In a docker run command, you can add multiple IP addresses for a single hostname. In a compose file, you can only set one IP per host.

docker run --rm --name tester --add-host myhost:0.0.0.1 --add-host myhost:0.0.0.2 alpine cat /etc/hosts

In a compose file, extra_hosts in long syntax won't pass validation if it sees duplicate keys. Short syntax will allow two hosts with the same IP, but overwrites any previous entries with the last entry for the same hostname.

services:
  tester:
    image: alpine
    container_name: tester
    extra_hosts:
      - "myhost=0.0.0.1"
      - "myhost=0.0.0.2"
    command: cat /etc/hosts