[Kea-users] ddns update question

Thomas Markwalder tmark at isc.org
Tue Oct 11 11:04:11 UTC 2016


On 10/10/16 1:23 PM, Richard Holbo wrote:
> Am doing my first deployment of KEA after using ISC-DHCP for..ever.
>
> Am trying to replicate an existing configuration with multiple subnets
> updating different forward DNS domains and am unclear on how to
> accomplish this as all examples/docs I've found only seem to use a
> single forward domain.
>
> I've got both forward and reverse working, forward for a single
> domain, and reverse for whatever the subnet is.  My issue seems to be
> the following commands:
>
> {
>
>   "dhcp-ddns": { "enable-updates": true,
>     "qualifying-suffix": "bogus.net <http://bogus.net>",
>     "override-client-update": true
> },
>
> These seem to be required in the DHCP4 config but then seem to
> override any settings in the ddns config
>
>   "forward-ddns" : {
>     "ddns-domains": [
>         {
>         "name": "bogus.net <http://bogus.net>.",
>         "dns-servers": [ { "ip-address": "re.dac.ted", "port": 53 } ]
>         },
>         {
>         "name": "wireless.bogus.",
>         "dns-servers": [ { "ip-address": "re.dac.ted", "port": 53 } ]
>         },
>         {
>          "name": "bogus.",
>          "dns-servers": [ { "ip-address": "re.dac.ted", "port": 53 } ]
>           },
>         ]
>     },
>
> The following is info is set under the "subnet" section for each:
> -----
>         {
>             "name": "domain-name",
>             "data": "bogus.net <http://bogus.net>"
>         },
> -----
>         {
>             "name": "domain-name",
>             "data": "bogus.wireless"
>         },
> -----
>         {
>             "name": "domain-name",
>             "data": "bogus"
>         },
>
> I'm sure it's something simple I'm missing but been banging my head
> against it for a couple of days.  All forward DNS goes to bogus.net
> <http://bogus.net> irrespective of the domain-name settings of the subnet.
>
> /thanks
> /rh
>
>
> _______________________________________________
> Kea-users mailing list
> Kea-users at lists.isc.org
> https://lists.isc.org/mailman/listinfo/kea-users

Hello Richard:


If I understand correctly, you're thinking that kea-dhcp4 will use the
"domain-name" option to qualify the hostname sent by your clients as the
FQDN for the DNS entries.  While this is a very useful feature, Kea does
not yet support it.  Currently, the dhcp server can only be configured
with a single, global qualifying-suffix.  It should be possible to
override this behavior by writing a custom hook for the lease4_select
hook point.  This hook point is called after the subnet has been
selected and a lease has been determined but before the DDNS request(s)
are created. The hook would need to create an FQDN option using the
domain-name value from the selected subnet and add the option to the
inbound packet, the "query" argument in the lease4_select.  The server
will see this FQDN option and use it when forming the DDNS requests sent
to kea-dhcp-ddns (aka D2).

Writing hooks is discussed in detail with examples in our developer's guide:

https://jenkins.isc.org/job/Fedora20_32_doxygen_doc/doxygen/de/df3/dhcpv4Hooks.html

In the meantime, I have opened a ticket in our Trac, to request the
behavior:

http://kea.isc.org/ticket/5048#ticket


Sincerely,

Thomas Markwalder

ISC Software Engineering










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