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

[Hillary Nelson]

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.

Running dhcp 4.3.2.

For example, I've added a new pool with 2001:beef:2:1018:f000::55a is new address, few mins later, client reports that address is already in use, and server marks the address as abandoned even with 'ignore declines' configured.

Jul 30 19:31:25 serverA dhcpd: Picking pool address 2001:beef:2:1018:f000::55a
Jul 30 19:31:25 serverA dhcpd: Advertise NA: address 2001:beef:2:1018:f000::55a to client with duid 00:01:00:01:18:eb:70:4f:18:03:73:33:6f:af iaid = 277917980 valid for 3600 seconds
Jul 30 19:33:35 serverA dhcpd: Picking pool address 2001:beef:2:1018:f000::55a
Jul 30 19:33:35 serverA dhcpd: Advertise NA: address 2001:beef:2:1018:f000::55a to client with duid 00:01:00:01:18:eb:70:4f:18:03:73:33:6f:af iaid = 277917980 valid for 3600 seconds

Then lots of messages like this:
Jul 30 19:36:41 serverA dhcpd: Client 00:01:00:01:18:eb:70:4f:18:03:73:33:6f:af reports address 2001:beef:2:1018:f000::55a is already in use by another host!
..
Jul 30 19:50:15 serverA dhcpd: Client 00:01:00:01:18:eb:70:4f:18:03:73:33:6f:af reports address 2001:beef:2:1018:f000::d3d is already in use by another host!
Jul 30 19:51:12 serverA dhcpd: Client 00:01:00:01:18:eb:70:4f:18:03:73:33:6f:af reports address 2001:beef:2:1018:f000::e43 is already in use by another host!

I wonder what caused client to report a fresh address in use, the same problem appear in version 4.3.1. Any help will be greatly appreciated!

Hillary

_______________________________________________
dhcp-users mailing list
[hidden email]
https://lists.isc.org/mailman/listinfo/dhcp-users

[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: [hidden email], phone: [phone]
_______________________________________________
dhcp-users mailing list
[hidden email]
https://lists.isc.org/mailman/listinfo/dhcp-users