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IPv6 Neighbor Discovery doesn't work between hosts in overlay #1169
IPv6 connectivity doesn’t seem to work between containers on different hosts in an overlay network. (I.e., currently in Docker 1.11.1 it seems to work only between containers on the same host, while IPv4 connectivity works also across hosts.)
Apparently the problem is that neighbor entries (within an overlay's namespace in each host) to containers on other hosts are created only for IPv4 addresses, but not for IPv6 addresses. Thus ARP works and returns addresses of containers on other hosts, but Neighbor Discovery doesn't.
Here's a simple example, where pinging a container on "host1" from another container on "host2" over IPv6 in a Swarm cluster fails, but works between containers within "host1" (DOCKER_HOST has been set to point to a Swarm manager in this example):
If the IPv6 addresses and corresponding MAC addresses of containers in other hosts are added as neighbors into the overlay’s namespace in each host, neighbor discovery and IPv6 connectivity across hosts start working. Example of a manual workaround:
@srcman It has been detected that this issue has not received any activity in over 6 months. Can you please let us know if it is still relevant: