Hello,

by default, DHCPv6 dhclient creates DUID-LL
if it is running in stateless mode (-6 -S) and
doesn't write it into leases file, most likely
because the DUID-LL is always generated the same.

It's however possible to specify DUID to be of type LLT instead of LL
with '-D LLT'. Rfc 3315 says that:
'Clients and servers using this type of DUID MUST
store the DUID-LLT in stable storage.'
That's not fulfiled in this case (-6 -S -D LLT),
because it's generated each time again.

It's not a big deal because the server doesn't store any
info about 'stateless' clients, so it doesn't matter
that the DUID-LLT is different each time.
But there's a TAHI test which tests this, i.e. that
DUID-LLT is still the same even in stateless mode.
It's a test DHCP_CONF.7.1.9, part B.
https://www.ipv6ready.org/docs/Phase2_DHCPv6_Conformance_Latest.pdf

With regards,
Jiri Popelka
Red Hat, inc.