Docker 28: IPv6 containers unreachable

Docker Engine General
1

I need help, I cant reach my IPv6 containers anymore.

Yesterday I updated docker on my debian system from v27.5.1 to 28.0.1:
docker-ce:amd64 (5:27.5.1-1~debian.12~bookworm, 5:28.0.1-1~debian.12~bookworm)

My daemon,json looks like this:

{
  "ipv6": true,
  "ip6tables": true,
  "fixed-cidr-v6": "2001:db8:1::/64"
}

I use a dedicated IPv6 subnet in my compose file to make my traefik container available:

networks:
  traefik_v6:
    name: traefik_v6
    enable_ipv6: true
    driver: bridge
    ipam:
      driver: default
      config:
        - subnet: 2a00:dead:beef:aaaa:1::/112

and assign a specific IPv6 to the container:

services:
  traefik:
    ...
    networks:
      traefik_v6:
        ipv6_address: 2a00:dead:beef:aaaa:1::2

To make it reachable I add a proxy:
ip neigh add proxy 2a00:dead:beef:aaaa:1::2 dev enp2s0
and set:
sysctl net.ipv6.conf.enp2s0.proxy_ndp=1

This always worked perfectly in prior to v28. No I don’t even know what to look for.
IPv4 containers are reachable just fine. Any help is much appreciated!

2

I might add, that containers that have not been assigned a dedicated IPv6 address (like the 2a00:dead:beef:aaaa:1::2 mentioned above) are accessible on the hosts enp2s0 IPv6 address.