Can you propose a patch for network manager to adjust test cases to this new
behavior? I'm wondering if there are other parts of network-manager that may
expect /64 instead of /128 and break existing users.
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dhclient incorrectly assumes a /64 ipv6 prefix
Status in isc-dhcp package in Ubuntu:
Status in network-manager package in Ubuntu:
Status in isc-dhcp source package in Precise:
Status in network-manager source package in Precise:
Status in isc-dhcp source package in Trusty:
Status in network-manager source package in Trusty:
Status in isc-dhcp source package in Xenial:
Status in network-manager source package in Xenial:
Status in isc-dhcp source package in Yakkety:
Status in network-manager source package in Yakkety:
Status in isc-dhcp package in Debian:
clients who get an ipv6 address from a dhcpv6 server assume the
address has a /64 prefix, but that is not necessarily true, and if the
subnet is different than /64 those clients will not be able to reach
other addresses in that /64 prefix because the other systems are not
on-link. This /64 assumption of dhclient effectively breaks the
client networking for certain addresses.
Set up a server with two interface nics, and one client connected to
each of those interfaces. On the server, set up a ipv6 subnet on each
interface, with a larger prefix than /64, e.g.:
configure dhcpv6 on the server, to provide ipv6 addresses on each
interface. Set the server as the default ipv6 route for the clients.
Allow the clients to get dhcpv6 ipv6 addresses from the server. The
clients will each get a ipv6 address with a /64 prefix, due to the bug
Try to ping (or otherwise communicate) between the clients. Since
they have /64 prefixes, they think they are on-link with each other,
but they are not, so they can't communicate.
After the dhclient bug is fixed, repeat the above setup, and the
clients will get /128 prefixes instead, and then will be able to
communicate with each other, because they will route the traffic to
each other through the server.
None. Non-standard (i.e. not /64) subnets served by dhcpv6 currently
are broken, this fixes that.
This is fixed in debian:
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