Host IPv6 address disappears when enabling Docker IPv6 Network

Open Source Projects DockerEngine
1

Hey there, maybe someone could give me a good advise to sort out the following issue
My Docker Host got its IPv6 settings automatically by DHCP but loses its IPv6 addresses when creating/using IPv6 Networks inside Docker.

Created the network with the following docker-compose parts:

version: '2.4'
networks:
  frontend:
    enable_ipv6: true
    ipam:
      config:
        - subnet: "fd00:0:0:0:3::/80"

Helped myself with a static entry in /etc/network/interfaces with the following, but it turned out that my public 2001: address stopped working and I would like to DHCP that again

iface enp0s31f6 inet6 static
      address 2001:a61:3a7c:8301:XXXX:XXXX:XXXX:XXXX
      netmask 64
      gateway 2001:a61:3a7c:8301:XXXX:XXXX:XXXX:XXXX
iface enp0s31f6 inet6 static
      address fd00::aaa1:XXXX:XXXX:XXXX
      netmask 64
      gateway fd00::2e91:XXXX:XXXX:XXXX

Ping on the gateway fd00::2e91:XXXX:XXXX:XXXX is working.

Some Sys-Infos:

# lsb_release -a
No LSB modules are available.
Distributor ID: Debian
Description:    Debian GNU/Linux 11 (bullseye)
Release:        11
Codename:       bullseye

# docker version
Client: Docker Engine - Community
 Version:           23.0.1
 API version:       1.42
 Go version:        go1.19.5
 Git commit:        a5ee5b1
 Built:             Thu Feb  9 19:46:54 2023
 OS/Arch:           linux/amd64
 Context:           default

Server: Docker Engine - Community
 Engine:
  Version:          23.0.1
  API version:      1.42 (minimum version 1.12)
  Go version:       go1.19.5
  Git commit:       bc3805a
  Built:            Thu Feb  9 19:46:54 2023
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.6.16
  GitCommit:        31aa4358a36870b21a992d3ad2bef29e1d693bec
 runc:
  Version:          1.1.4
  GitCommit:        v1.1.4-0-g5fd4c4d
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0
2

What happens if you use fd00::/64 for your docker network?

Ipv6 needs 64bit network or smaller (actually bigger ranger) to work properly. Networks with more bits (actually smaller range) mix the network bits with the node bits and things break.