Improve the documentation about network

[craph]

trafficstars

Is this a docs issue?

• [X] My issue is about the documentation content or website

Type of issue

I can't find what I'm looking for

Description

Is it possible to have a page where is it explain how networking / bridge mode works and how IP addresses are given. With details of what are :

• bip
• fixed-cidr
• what is the size vs the base in the default-address-pools
• what is the link between bip and base in default-address-pools

Location

https://docs.docker.com

Suggestion

No response

[polarathene]

Below is from recall, but should be easy enough for you to verify and respond with any corrections 👍

---

• what is the size vs the base in the default-address-pools

Separate PR related to that: https://github.com/docker/docs/issues/18782

The base defines a range that is split into subnets of size.

You might like this article on the topic: https://straz.to/2021-09-08-docker-address-pools/

---

• bip
• fixed-cidr

From the dockerd docs: https://docs.docker.com/engine/reference/commandline/dockerd/#daemon

--fixed-cidr string IPv4 subnet for fixed IPs --bip string Specify network bridge IP

You can choose your own subnet to use for the legacy default bridge (docker0) with fixed-cidr, while bip AFAIK appears commonly set as the gateway address for that subnet.

You'll probably find bip defaults appropriately without setting it explicitly, it's only there if you know that you need to change it.

---

• what is the link between bip and base in default-address-pools

If you don't set fixed-cidr, then AFAIK when the daemon starts it'll take the first available subnet from the default pools? Then the bip should default to the first available address in that subnet.

EDIT: 172.16.0.0/16 doesn't seem to be in default-address-pools, so I guess that default is configured elsewhere.

• I was recalling when I added IPv6 pools and enabled IPv6 on the default bridge it pulled from that IIRC.
• If this other subnet is in use (eg: by a VM guest), then I think Docker will still fallback to pulling a new subnet from the default-address-pools.

[docker-robot[bot]]

There hasn't been any activity on this issue for a long time. If the problem is still relevant, mark the issue as fresh with a /remove-lifecycle stale comment. If not, this issue will be closed in 14 days. This helps our maintainers focus on the active issues.

Prevent issues from auto-closing with a /lifecycle frozen comment.

/lifecycle stale

[docker-robot[bot]]

Closed issues are locked after 30 days of inactivity. This helps our team focus on active issues.

If you have found a problem that seems similar to this, please open a new issue.

/lifecycle locked