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16th chunk of `content/manuals/engine/release-notes/28.md`
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- When a port mapping includes a host IP address or port number that cannot be used because NAT from the host is disabled using `--gateway_mode_ipv[46]`, container creation will no longer fail. The unused fields may be needed if the gateway endpoint changes when networks are connected or disconnected. A message about the unused fields will be logged. [moby/moby#48575](https://github.com/moby/moby/pull/48575)
- Do not create iptables nat-POSTROUTING masquerade rules for a container's own published ports, when the userland proxy is enabled. [moby/moby#48854](https://github.com/moby/moby/pull/48854)

#### IPv6

- Add `docker network create` option `--ipv4`. To disable IPv4 address assignment for a network, use `docker network create --ipv4=false [...]`. [docker/cli#5599](https://github.com/docker/cli/pull/5599)
- Daemon option `--ipv6` (`"ipv6": true` in `daemon.json`) can now be used without `fixed-cidr-v6`. [moby/moby#48319](https://github.com/moby/moby/pull/48319)
- IPAM now handles subnets bigger than "/64". [moby/moby#49223](https://github.com/moby/moby/pull/49223)
- Duplicate address detection (DAD) is now disabled for addresses assigned to the bridges belonging to bridge networks. [moby/moby#48609](https://github.com/moby/moby/pull/48609)
- Modifications to `host-gateway`, for compatibility with IPv6-only networks. [moby/moby#48807](https://github.com/moby/moby/pull/48807)
  - When special value `host-gateway` is used in an `--add-host` option in place of an address, it's replaced by an address on the Docker host to make it possible to refer to the host by name. The address used belongs to the default bridge (normally `docker0`). Until now it's always been an IPv4 address, because all containers on bridge networks had IPv4 addresses.
  - Now, if IPv6 is enabled on the default bridge network, `/etc/hosts` entries will be created for IPv4 and IPv6 addresses. So, a container that's only connected to IPv6-only networks can access the host by name.
  - The `--host-gateway-ip` option overrides the address used to replace `host-gateway`. Two of these options are now allowed on the command line, for one IPv4 gateway and one IPv6.
  - In the `daemon.json` file, to provide two addresses, use `"host-gateway-ips"`. For example, `"host-gateway-ips": ["192.0.2.1", "2001:db8::1111"]`.


### Bug fixes and enhancements

- Add IPv6 loopback address as an insecure registry by default. [moby/moby#48540](https://github.com/moby/moby/pull/48540)
- Add support for Cobra-generated completion scripts for `dockerd`. [moby/moby#49339](https://github.com/moby/moby/pull/49339)
- Fix DNS queries failing when containers are launched via `systemd` auto-start on boot [moby/moby#48812](https://github.com/moby/moby/pull/48812)
- Fix Docker Swarm mode ignoring `volume.subpath` [docker/cli#5833](https://github.com/docker/cli/pull/5833)
- Fix `docker export` continuing the export after the operation is canceled. [moby/moby#49265](https://github.com/moby/moby/pull/49265)
- Fix `docker export` not releasing the container's writable layer after a failure. [moby/moby#48517](https://github.com/moby/moby/pull/48517)
- Fix `docker images --tree` unnecessary truncating long image names when multiple names are available [docker/cli#5757](https://github.com/docker/cli/pull/5757)
- Fix a bug where a container with a name matching another container's ID is not restored on daemon startup. [moby/moby#48669](https://github.com/moby/moby/pull/48669)
- Fix an issue preventing some IPv6 addresses shown by `docker ps` to be properly bracketed [docker/cli#5468](https://github.com/docker/cli/pull/5468)
- Fix bug preventing image pulls from being cancelled during `docker run`. [docker/cli#5645](https://github.com/docker/cli/pull/5645)
- Fix error-handling when running the daemon as a Windows service to prevent unclean exits. [moby/moby#48518](https://github.com/moby/moby/pull/48518)
- Fix issue causing output of `docker run` to be inconsistent when using `--attach stdout` or `--attach stderr` versus `stdin`.  `docker run --attach stdin` now exits if the container exits. [docker/cli#5662](https://github.com/docker/cli/pull/5662)
Title: Docker Enhancements: Networking, IPv6 Improvements, and Bug Fixes
Summary
This section details improvements in Docker, including networking enhancements where container creation won't fail if port mappings include unusable host IP addresses due to disabled NAT, and masquerade rules are no longer created for published ports with userland proxy. It introduces the `--ipv4` option for `docker network create` to disable IPv4 assignment and allows using `--ipv6` without `fixed-cidr-v6`. The update improves IPAM for larger subnets, disables duplicate address detection for bridge networks, and modifies host-gateway compatibility for IPv6-only networks. Also includes bug fixes such as adding IPv6 loopback address as an insecure registry, fixing DNS queries for systemd auto-start containers, fixing Docker Swarm mode's handling of volume subpaths, addressing issues with `docker export`, `docker images --tree`, container restoration, IPv6 address display, image pull cancellation, Windows service error handling, and the consistency of `docker run` output.