I’ve got an IKEA Symfonisk table lamp. I noticed that at some point it has started to request an IPv6 address via DHCPv6, but it’s doing so with an invalid non-unique DUID (DHCP Unique Identifier).
The DUID it’s using is (in hex): 00030001000000000000
Decoded, that is a DUID “type 3” (DUID based on link-layer address), with the address type set to Ethernet… but where it should contain the Ethernet MAC address, instead the DUID is set to all zeros.
I expect that this non-unique ID might cause problems if someone has multiple Sonos devices in a network with DHCPv6 enabled, although the exact result depends on what DHCP server is in use.
For reference, my speaker is currently running the Sonos OS S2, Version 80.1-56190. It is connected via Ethernet cable (WiFi is disabled).