Static IPv6 adress on multiple interfaces


I’m currently trying to set up a container running Debian 10 (amd64) which should be connected to multiple interfaces. Because I want to short and simple addresses I want them to be static. So I configured them as mentioned in other posts about a static IP configuration in LXD. I also enabled DHCPv6 in Debian through the /etc/network/interfaces file.
For the first bridge (lxdbr0) everything works fine. But for the second manually created bridge it does not work as expected. While the IPv4 address is assigned correctly, the IPv6 address only has only the correct prefix but uses a custom suffix.
The same problem with IPv6 occurs when I try to configure a static IPv6 address directly inside the container through the /etc/network/interfaces file, which also only shows up for every ip address except the first one. Here I’m also interested if this type of static configuration is also considered as a bad practise when using LXD (because I never saw someone recommending this type of setup for static ips in LXD).

/etc/network/interfaces (with DHCPv6) file

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp
iface eth0 inet6 dhcp

auto eth1
iface eth1 inet dhcp
iface eth1 inet6 dhcp

source /etc/network/interfaces.d/*.cfg

cbr0 bridge configuration (not lxdbr0)

  ipv4.dhcp: "true"
  ipv4.nat: "true"
  ipv6.address: fd00:fffd::1/64
  ipv6.dhcp: "true"
  ipv6.dhcp.stateful: "true"
  ipv6.nat: "true"
description: ""
name: cbr0
type: bridge
- /1.0/instances/c1
managed: true
status: Created
- none

container config

architecture: x86_64
  boot.autostart: "true"
  boot.autostart.priority: "13"
  image.architecture: amd64
  image.description: Debian buster amd64 (20200601_05:24)
  image.os: Debian
  image.release: buster
  image.serial: "20200601_05:24"
  image.type: squashfs
  volatile.base_image: d85d43dc0ad4763c05b79b62b7fe9a53d0784d8a65856a5adda752cb75da0450
  volatile.eth0.host_name: vetha3086490
  volatile.eth0.hwaddr: 00:16:3e:52:86:31
  volatile.eth1.host_name: veth5d10a2d9
  volatile.eth1.hwaddr: 00:16:3e:fb:4d:98
  volatile.idmap.base: "0"
  volatile.idmap.current: '[{"Isuid":true,"Isgid":false,"Hostid":1000000,"Nsid":0,"Maprange":65536},{"Isuid":false,"Isgid":true,"Hostid":1000000,"Nsid":0,"Maprange":65536}]' '[{"Isuid":true,"Isgid":false,"Hostid":1000000,"Nsid":0,"Maprange":65536},{"Isuid":false,"Isgid":true,"Hostid":1000000,"Nsid":0,"Maprange":65536}]'
  volatile.last_state.idmap: '[{"Isuid":true,"Isgid":false,"Hostid":1000000,"Nsid":0,"Maprange":65536},{"Isuid":false,"Isgid":true,"Hostid":1000000,"Nsid":0,"Maprange":65536}]'
  volatile.last_state.power: RUNNING
    ipv6.address: fd00:1::12
    name: eth0
    nictype: bridged
    parent: lxdbr0
    type: nic
    ipv6.address: fd00:fffd::10
    name: eth1
    nictype: bridged
    parent: cbr0
    type: nic
ephemeral: false
- default
stateful: false
description: ""