Custom outgoing IP from docker container

Hi. If You want to configure a custom docker container to use one public IPs that are located on the host system You can use this schema.

First, need install docker engine on the system  - install docker 
Next, create docker networks like this

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docker network create --attachable --opt 'com.docker.network.bridge.name=my-network-1' --opt 'com.docker.network.bridge.enable_ip_masquerade=false' --subnet=172.20.10.0/24 --gateway=172.20.10.1 my-network-1

docker network create --attachable --opt 'com.docker.network.bridge.name=my-network-2' --opt 'com.docker.network.bridge.enable_ip_masquerade=false'  --subnet=172.20.20.0/24 --gateway=172.20.20.1 my-network-2

docker network create --attachable --opt 'com.docker.network.bridge.name=my-network-3' --opt 'com.docker.network.bridge.enable_ip_masquerade=false' --subnet=172.20.30.0/24 --gateway=172.20.30.1 my-network-3

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One important option for that is --opt 'com.docker.network.bridge.enable_ip_masquerade=false', that option disable the MASQUERADE which is enabled as default. After that, You need add iptables rule for POSTROUTING NAT table 

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iptables -t nat -A POSTROUTING -s 172.20.10.0/24 ! -o my-network-1 -j SNAT --to-source xxx.xxx.xxx.xxx

iptables -t nat -A POSTROUTING -s 172.20.20.0/24 ! -o my-network-2 -j SNAT --to-source xxx.xxx.xxx.xxx

iptables -t nat -A POSTROUTING -s 172.20.30.0/24 ! -o my-network-3 -j SNAT --to-source  xxx.xxx.xxx.xxx

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After that, You can start Your containers with docker compose command and docker-compose.yml

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version: '3'

services:

  container1:

    image: nginx

    networks:

      my-network-1:

        

    

  container2:

    image: nginx

    networks:

      my-network-2:

      

  container3:

    image: nginx

    networks:

      my-network-3:

      

networks:

  my-network-1:

    external: true

  my-network-2:

    external: true

  my-network-3:

    external: true

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That's all.
Bye.