IPv6 Support

Calico supports connectivity over IPv6, between compute hosts, and between compute hosts and their VMs. This means that, subject to security configuration, a VM can initiate an IPv6 connection to another VM, or to an IPv6 destination outside the data center; and that a VM can terminate an IPv6 connection from outside.

Requirements for containers

Containers have no specific requirements for utilising IPv6 connectivity.

Implementation details

Following are the key points of how IPv6 connectivity is currently implemented in Calico.

  • IPv6 forwarding is globally enabled on each compute host.
  • Felix (the Calico agent):
    • does ip -6 neigh add lladdr dev, instead of IPv4 case arp -s, for each endpoint that is created with an IPv6 address
    • adds a static route for the endpoint’s IPv6 address, via its tap or veth device, just as for IPv4.
  • Dnsmasq provides both Router Advertisements and DHCPv6 service (neither of which are required for container environments).
    • Router Advertisements, without SLAAC or on-link flags, cause each VM to create a default route to the link-local address of the VM’s TAP device on the compute host.
    • DHCPv6 allows VMs to get their orchestrator-allocated IPv6 address.
  • For container environments, we don’t Dnsmasq:
    • rather than using Router Advertisements to create the default route, we Proxy NDP to ensure that routes to all machines go via the compute host.
    • rather than using DHCPv6 to allocate IPv6 addresses, we allocate the IPv6 address directly to the container interface before we move it into the container.
  • BIRD6 runs between the compute hosts to distribute routes.