viiftw · March 26, 2024 04:51 · Jan 2, 2020 · Jan 2, 2020
diff --git a/overlay-network-and-static-ips-for-docker-containers.md b/overlay-network-and-static-ips-for-docker-containers.md
@@ -1,9 +1,11 @@
-I don't expect https://github.com/moby/moby/issues/24170 to be implemented on near future so this gist is about looking for least ugly workarounds which are available today and on near future.
+I don't expect [moby/moby#24170](https://github.com/moby/moby/issues/24170) to be solved by Docker team on near future so this gist is about looking for least ugly workarounds which are available today and on near future.
 
 # What is possible on Docker 19.03
 ## Network
-It is possible to create overlay network with use specified subnet.
-On this example I create network which is size is two C -class networks ( IP range 10.0.0.0 - 10.0.1.255 ) and force Docker to use IPs from second part of it ( 10.0.1.0 - 10.0.1.255 ).
+It is possible to create overlay network with use user specified subnet.
+On this example I create network which is size is two C -class networks ( IP range 10.0.0.0 - 10.0.1.255 )
+and force Docker to use IPs from second part of it ( 10.0.1.0 - 10.0.1.255 ).
+
 That way I can make sure that IPs 10.0.0.2 - 10.0.0.254 can be specified to containers and they do not collide with IPs which Docker engine assign for service(s)/container(s).
 ```bash
 docker network create --driver overlay --subnet 10.0.0.0/23 --ip-range 10.0.1.0/24 --gateway 10.0.0.1 --attachable test
@@ -52,7 +54,7 @@ Above solution solves two issues:
 - It allow containers communicate between Docker nodes using overlay network.
 
 However those containers are not swarm services which means that you lose some control to them.
-Luckily I have already implemented https://github.com/docker/cli/pull/1940 and I'm expecting that it will get merged and released as part of next Docker version.
+Luckily I have already implemented [docker/cli#1940](https://github.com/docker/cli/pull/1940) and I'm expecting that it will get merged and released as part of next Docker version.
 
 That makes possible to use swarm stack like this:
 ```yaml

diff --git a/overlay-network-and-static-ips-for-docker-containers.md b/overlay-network-and-static-ips-for-docker-containers.md
@@ -0,0 +1,86 @@
+I don't expect https://github.com/moby/moby/issues/24170 to be implemented on near future so this gist is about looking for least ugly workarounds which are available today and on near future.
+
+# What is possible on Docker 19.03
+## Network
+It is possible to create overlay network with use specified subnet.
+On this example I create network which is size is two C -class networks ( IP range 10.0.0.0 - 10.0.1.255 ) and force Docker to use IPs from second part of it ( 10.0.1.0 - 10.0.1.255 ).
+That way I can make sure that IPs 10.0.0.2 - 10.0.0.254 can be specified to containers and they do not collide with IPs which Docker engine assign for service(s)/container(s).
+```bash
+docker network create --driver overlay --subnet 10.0.0.0/23 --ip-range 10.0.1.0/24 --gateway 10.0.0.1 --attachable test
+```
+
+## Containers
+By default containers IP addresses are controlled by Docker engine and those cannot be changed inside of container.
+Luckily that behavior can be overridden by adding `NET_ADMIN` capability for container.
+
+### Custom Docker image
+So first we need create custom docker image which is able set IP for container when it starts.
+That we can do example with Dockerfile like this:
+```
+FROM ubuntu
+RUN apt-get update \
+        && apt-get install -y net-tools iputils-ping
+COPY /start.sh /
+ENTRYPOINT /start.sh
+```
+and start script like this:
+```bash
+#!/bin/bash
+if [[ -f "${STATIC_IP}" ]]; then
+        echo "Using default IP from Docker"
+else
+        echo "Found static IP: ${STATIC_IP} using it"
+        ifconfig eth0 ${STATIC_IP} netmask 255.255.255.0 up
+fi
+sleep infinity
+```
+Then just build that with command:
+```bash
+docker build . -t static-ip
+```
+
+### Starting container
+Then we can start two containers with commands like these which connects then to overlay network and changes IP addresses inside of the to static ones.
+```bash
+docker run --name test1 --detach=true --rm --cap-add=NET_ADMIN --network=test -e STATIC_IP=10.0.0.11 static-ip
+docker run --name test2 --detach=true --rm --cap-add=NET_ADMIN --network=test -e STATIC_IP=10.0.0.12 static-ip
+```
+
+# What will be possible on next version
+Above solution solves two issues:
+- It sets static IPs for containers.
+- It allow containers communicate between Docker nodes using overlay network.
+
+However those containers are not swarm services which means that you lose some control to them.
+Luckily I have already implemented https://github.com/docker/cli/pull/1940 and I'm expecting that it will get merged and released as part of next Docker version.
+
+That makes possible to use swarm stack like this:
+```yaml
+version: "3.7"
+services:
+  test1:
+    image: static-ip
+    environment:
+      STATIC_IP: 10.0.0.11
+    networks:
+      - test
+    cap_add:
+      - NET_ADMIN
+  test2:
+    image: static-ip
+    environment:
+      STATIC_IP: 10.0.0.12
+    networks:
+      - test
+    cap_add:
+      - NET_ADMIN
+
+networks:
+  test:
+   external: true
+   name: test
+```
+and deploy it with command:
+```bash
+docker stack deploy -c static-ip.yml static-ip
+```