DHCPv6 accounting

[Tim Chown]

On 21 May 2013, at 21:06, Brian E Carpenter <brian.e.carpenter at gmail.com> wrote:

> On 22/05/2013 04:20, Phil Mayers wrote:
>> On 21/05/13 16:58, Tim Chown wrote:
>> 
>>> I would suspect in a largeish enterprise that that approach would be
>>> appropriate, as it's likely that all DHCPv6 traffic would be forwarded
>>> by a relay.
>> 
>> Except unicast traffic of course, unless the relays are expected to
>> interfere with such as well. This means the DHCP server will need to
>> stash the relay options (a common problem with DHCP option 82).
>> 
>> It's also worth asking whether DHCPv6 server operators would like to
>> know the source layer2 info as the relay saw it, as the client claims
>> it, or both.
> 
> In any case, the ground truth in IPv6 can surely only be found
> in the ND cache? It is not a safe assumption that all addresses
> were assigned by DHCPv6.

As I understood it, the implied requirement here was to be able to track DHCP allocations for IPv6 in a similar model as used for IPv4 today.

In practice, we chose not to do that and instead use an open source package to query our switch and router devices to build a database of IP/MAC/port mappings for L2/L3 address accountability. Which is I recall exactly what Phil mentioned. That's worked pretty well for us so far.

I also recall there's a personal IETF draft suggesting use of DHCP for a router to report addresses seen via ND on a link.

Tim