[kea-dev] Leasing from multiple IPv4 subnets to the same relay

[Guido Marelli]

Hi Marcin, thank you for clarifying.

On the other hand, a scenario that I have observed in many deployments with
DHCPv4, is the existence of multiple networks configured in the same
relay/CMTS that are eligible for leasing to the same type of device. This
is: there is no difference between networks A, B and C but any of these
networks can be use to assign addresses, for example, to CPEs.

>From your comments, I understand that this is now not possible with Kea: Do
you plan to include this type of functionality?


Guido Marelli
Intraway Corp.
Project Leader
AR Office: +54 (11) 6040 4000 x4033
US Office: +1 (516) 620 3890 X4033

Mobile: +54 (911) 5424 9574
Email: guido.marelli at intraway.com


Visit our website at http://www.intraway.com
Proud to be an ISO 9001:2008 certified company


On Thu, Nov 12, 2015 at 6:25 AM, Marcin Siodelski <marcin at isc.org> wrote:

>
> On 10.11.2015 17:00, Guido Marelli wrote:
> > Hi,
> >
> > I'm analyzing the feasibility of using Kea in DOCSIS networks. However,
> > I didn't managed to configure Kea to use more than one IPv4 subnet with
> > the same relay/giaddr.
> >
> > What I observed is that Kea depletes leases from the first subnet and
> > that the other subnets, which were configured with the same relay, are
> > ignored. I think this behavior is due to the method "CfgSubnets4 ::
> > selectSubnet" which iterates subnets until it finds the first subnet
> > that matches the giaddr, but it doesn't check lease availability.
> >
> > Any thoughts on this?
> >
> >
> > Regards,
> > Guido
> >
> >
> > Guido Marelli
> > Intraway Corp.
> > Project Leader
> > AR Office: +54 (11) 6040 4000 x4033
> > US Office: +1 (516) 620 3890 X4033
> >
> > Mobile: +54 (911) 5424 9574
> > Email: guido.marelli at intraway.com <mailto:guido.marelli at intraway.com>
> >
> >
> > Visit our website at http://www.intraway.com <http://www.intraway.com/>
> > Proud to be an ISO 9001:2008 certified company
> >
> >
> >
>
> Hi Guido,
>
> Thanks for your email and your interest in Kea.
>
> We have implemented "limited" support for DOCSIS in 2013 and
> successfully tested it with one cable network. This limited support
> facilitates the case when devices connected to the same link obtain
> addresses from different subnets. The devices are differentiated by the
> contents of the Vendor Class Identifier. It is assumed that that a
> device is a CM if the identifier is "docsis3.0". It is assumed that the
> device is a router if the identifier is "eRouter1.0".
>
> As per the Kea User's Guide:
> http://kea.isc.org/docs/kea-guide.html#dhcp4-client-classifier
>
> you can create a subnet with address pools dedicated exclusively for CMs
> with a configuration similar to this:
>
> "Dhcp4": {
>     "subnet4": [
>         {
>             "subnet": "192.0.2.0/24",
>             "pools": [ { "pool": "192.0.2.10 - 192.0.2.20" } ],
>             "relay": {
>                 "ip-address": "10.0.0.1"
>             },
>             "client-class": "VENDOR_CLASS_docsis3.0"
>         }
>     ],
>     ...
> }
>
> Note that the "docsis3.0" is an identifier sent in the Vendor Class
> Identifier option by CM. If your CMs send different identifier, the
> class name is "VENDOR_CLASS_<your-cm-identifier>".
>
> One final note. The "proper" implementation of DOCSIS requires full
> support for client classification, i.e. the server must be able to
> extract arbitrary expressions from various DHCP options and use them to
> assign a client to a particular class or set of classes. Then, classes
> are used to assign subnets, options etc according to the configuration.
> The first part of this generic client classification will be available
> with the Kea1.0 release (December 2015). The next release (Kea1.1) is
> fully devoted to finish up client classification. So, if the current
> "limited" support for DOCSIS is not sufficient for your deployment, you
> may wish to monitor the progress on client classification for 1.0 and
> 1.1 releases to make sure it would address your needs.
>
> I should also note that Kea has a built-in mechanism of "hooks" which
> allows for customizing packet processing at various stages. The server
> calls out to custom/user-defined C++ library to perform common tasks
> like subnet selection, options assignment etc. It is possible for you to
> create a simple C++ library which replaces standard subnet selection
> mechanism with customized one, required in your deployment.
>
> More about writing your own hooks can be found in Kea Developer's Guide:
>
> http://git.kea.isc.org/~tester/kea/doxygen/df/d46/hooksdgDevelopersGuide.html
>
> Marcin Siodelski
> DHCP Software Engineer
> ISC
>
>
>
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