DHCPv6 client report fresh address in use and server ignore 'ignore declines'

[Jay Ford]

On Thu, 30 Jul 2015, Hillary Nelson wrote:
> We moved some of our networks from SLAAC to DHCPv6 today, and there are 
> tons of log with client complaining that addresses being used while they 
> are not.

Look for duplicate DUIDs among the clients (often due to imaging/cloning). 
The server will see all clients with the same DUID as the same device & thus 
provide the same IPv6 address, which creates a duplicate address situation 
for the clients.

The logging by the server isn't very helpful for this type of problem (or
many others), but increasing the debug level in the server helps a little.
I've complained to ISC about several aspects of the DHCPv6 logging & opened a
few bugs about it, resulting in some improvement, but it's still much worse
than the DHCPv4 logging.

________________________________________________________________________
Jay Ford, Network Engineering Group, Information Technology Services
University of Iowa, Iowa City, IA 52242
email: jay-ford at uiowa.edu, phone: 319-335-5555