Quick note; the Docker Community slack is on a free plan, which means that Slack conversations will eventually disappear. Not sure if there's anything relevant in the slack thread that must be preserved, but if there is, it's worth to either copy (or screenshot) the relevant discussion.

Quick note; the Docker Community slack is on a free plan, which means that Slack conversations will eventually disappear. Not sure if there's anything relevant in the slack thread that must be preserved, but if there is, it's worth to either copy (or screenshot) the relevant discussion.

Oh, thank you - hadn't appreciated that. I think it's mostly here, apart from Vinod's repro steps ...

vinod kumar 14 days ago

I believe I found the problem . we create dockerbr using manual configuration . then using old style network-script to bringup the interface up and down and also to persist the information for restart case. here is the script .

# Tue Apr 23 05:27:59 2024

DEVICE=dockerbr
TYPE=Bridge
IPADDR=172.16.2.1
NETMASK=255.255.0.0
MTU=1450
ONBOOT=yes
BOOTPROTO=none
NM_CONTROLLED=no
DELAY=0
NOZEROCONF=yes
IPV6INIT=yes
IPV6ADDR=fddd::2:0/96
IPV6_DEFAULTGW=::dockerbr

here we assign both IPv6 and IPV4 address.
when docker comes up it reassign the IPV6 based on assign CIDR . here is the command-line that is being used for bring up the dockerd.

/usr/bin/dockerd --exec-opt native.cgroupdriver=systemd --userland-proxy-path=/usr/bin/docker-proxy -H unix:///var/run/docker.sock -H tcp://172.16.2.1:2375 --data-root /opt/ciena/data/docker --label host_id=2 --fixed-cidr=172.16.2.0/24 --bridge dockerbr4 --mtu 1450 --ipv6 --fixed-cidr-v6=fddd::2:0/112

i guess they both are conflicting and breaking ipv6 connectivity when interface brought down and up in later stage.
Note: I dont know if its wrong or right but this used to work before 25.x release.

vinod kumar [12 days ago]

hi Rob , here are the steps to recreate issue . pls note that we use vxilan to connect with adjacent hosts docker network.

systemctl stop docker
sudo route -6 del fddd::/96 dev dockerbr
ifconfig dockerbr down
brctl delbr dockerbr
rm -f /opt/ciena/data/docker/docker/network/files/local-kv.db

# create everything from scratch

bridge fdb del to 00:00:00:00:00:00 dst 10.182.39.162 dev vxilan
bridge fdb del to 00:00:00:00:00:00 dst 10.182.39.160 dev vxilan
ifconfig vxilan down
ip link del vxilan

sudo ip link add vxilan type vxlan id 42 dev ens192 dstport 0
sudo brctl addbr dockerbr"
sudo brctl addif dockerbr vxilan || sudo brctl show dockerbr | grep vxilan
sudo ifconfig vxilan 0 up"
sudo ifconfig dockerbr 172.16.2.1/16 up
sudo ifconfig vxilan mtu 1450
sudo bridge fdb append to 00:00:00:00:00:00 dst 10.182.39.162 dev vxilan
sudo bridge fdb append to 00:00:00:00:00:00 dst 10.182.39.160 dev vxilan
sudo route -6 add fddd::/96 dev dockerbr
systemctl start docker
docker network create --driver bridge --subnet 172.16.0.0/16 --gateway 172.16.2.1 --ip-range 172.16.2.0/24 --ipv6 --subnet fddd::/96 --gateway fddd::2:1 --ip-range fddd::2:0/112 --label bp={} -o "com.docker.network.bridge.name"="dockerbr" -o "com.docker.network.driver.mtu"="1450" bp-bridge

# now start container and start ipv6 ping . choose ipv6 ping-able from the host.

docker run --rm  --net bp-bridge -it alpine  sh -c "ping6 2620:11b:d06c:f801:20c:29ff:fe12:cab0"

# command for running dokcerd

/usr/bin/dockerd --exec-opt native.cgroupdriver=systemd --userland-proxy-path=/usr/bin/docker-proxy -H unix:///var/run/docker.sock -H tcp://172.16.0.1:2375 --data-root /opt/ciena/data/docker --label host_id=2 

ping6 will stop after some duration.