Docker Default Address Pool

Author: mstathers

_posts/2023-08-14-docker-default-address-pool.md

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+---
+layout: posts
+title: Docker Default Address Pool
+---
+
+Every time a [Docker Compose](https://docs.docker.com/compose/){:target=_blank} application starts it creates a [Docker network](https://docs.docker.com/network/){:target=_blank} to facilitate inter-container communication. I encountered a problem where sometimes the network assigned to the application would conflict with services running on our internal network. Troubleshooting this is a different discussion, but the fix is straightforward, the default address pool from which Docker assigns new Docker networks needs to change.
+
+In a server environment edit the `/etc/docker/daemon.json` file. For Docker Desktop, this can be modified via the Docker Engine menu found within the Settings. Add the following block to the existing config:
+```
+  "default-address-pools": [
+    {
+      "base": "10.10.0.0/16",
+      "size": 24
+    }
+```
+Note that this configuration adheres JSON format.
+
+The above configuration sets up a single address pool of `10.10.0.0/16` affording over 65,000 IP addresses. Each network created within this pool will use a `/24` CIDR subnet mask effectively providing 254 usable IP addresses. For my own requirements, this allocation proves more than adequate, and should ensure I have no more IP conflicts.
+
+It is possible to configure multiple address pools if desired.
+
+When choosing an address pool, exercise caution to try to avoid address conflicts. To illustrate, my home network uses a `192.168.x.x` address, and my workplace's internal network uses portions of the `172.` private range. By opting to choose a network inside the `10.x.x.x` range I expect to avoid any conflicts moving ahead. For more information on IPv4 ranges reserved for private use, reference [https://en.wikipedia.org/wiki/Private_network](https://en.wikipedia.org/wiki/Private_network){:target=_blank}.