[Kea-users] DDNS update for win10 clients

[Thomas Markwalder]

Hello Dominik:

Your Windows client is sending up the FQDN option (81) in it's REQUEST:

>
> 10:21:35.722392 IP (tos 0x0, ttl 128, id 8385, offset 0, flags [none],
> proto UDP (17), length 335)
>     0.0.0.0.68 > 255.255.255.255.67: [udp sum ok] BOOTP/DHCP, Request
> from bc:83:85:25:f6:6a, length 307, xid 0xef706b5a, Flags [Broadcast]
> (0x8000)
>           Client-Ethernet-Address bc:83:85:25:f6:6a
>           Vendor-rfc1048 Extensions
>             Magic Cookie 0x63825363
>             DHCP-Message Option 53, length 1: Request
>             Client-ID Option 61, length 7: ether bc:83:85:25:f6:6a
>             Requested-IP Option 50, length 4: 192.168.1.104
>             Server-ID Option 54, length 4: 192.168.1.10
>             Hostname Option 12, length 5: "APFEL"

>             FQDN Option 81, length 8: "APFEL"          

>             Vendor-Class Option 60, length 8: "MSFT 5.0"
>             Parameter-Request Option 55, length 13:
>               Subnet-Mask, Default-Gateway, Domain-Name-Server,
> Domain-Name
>               Router-Discovery, Static-Route, Vendor-Option,
> Netbios-Name-Server
>               Netbios-Node, Netbios-Scope, Classless-Static-Route,
> Classless-Static-Route-Microsoft
>               Option 252
>             END Option 255, length 0
>
This options contains both the name the client wishes to use, along with
the NOS flags.   Kea DHCP servers use these flags along with
configuration parameters to determine which if any updates to request. 
While the printed dump does not show flag values I would surmise that
both N and S flags are 0 which indicate that the client is requesting to
do its own Forward DNS updates (see
http://kea.isc.org/docs/kea-guide.html#dhcp4-ddns-config  section 
8.2.16.2. When Does the kea-dhcp4 Server Generate DDNS Requests, for a
more detailed explanation).

If you cannot alter what your client is sending, you can override this:

"Dhcp4": {
    "dhcp-ddns": {
        *|"override-client-update": true|*,
        ...
    },
    ...
}

However this will override the flags for all clients. 
Note that your Android clients are not sending the FQDN option.

Regards,

Thomas Markwalder
ISC Software Engineering