[Kea-users] Handling of Prefixdelegation hints

[Ede Wolf]

Hello,

new to kea I am having a /56 network, that is being delegated downstream 
by kea in two /57 nets.
Kea seems to assign those two subnets in a round robin fashion to 
clients, so to have a group of clients receiving a certain subnet, I am 
using prefix hints containing the netid desired with the /57 length.

According to my limited understanding of wireshark, those hints are 
being sent by the client, but seemingly ignored by kea.

The question is, is this likely to be a misconfiguration or sloppieness 
on my side or just works as designed? I have found astonishingly little 
about prefix hints and kea, but maybe my google skills lack as well.

I am running kea-2.2 as shipped by debian 12

 From the client solicit:
A Prefix
     Option: IA Prefix (26)
     Length: 25
     Preferred lifetime: 0
     Valid lifetime: 0
     Prefix length: 57
     Prefix address: 2001:dead:beef:aa00::


But from the server logs:
DEBUG DHCP6_PROCESS_IA_PD_REQUEST duid=[00:..], tid=0x..: server is 
processing IA_PD option with iaid=.. and hint=2001:dead:beef:aa80::


And of course that upper aa80 net is finally being delegated, despite 
the client requesting the lower of the two. And this is a 
testenvironment, so the pools are certainly not exhausted. Would be kind 
of impossible anyway.

The subnet configuration is pretty much bare minimum:

{
         "subnet": "fde1:dead:beef:16::/64",
         "interface": "eth0",
         "id": 11,
         "pools": [ { "pool":  "fde1:dead:beef:16::12 - 
fde1:dead:beef:16::ffba" } ],
         "pd-pools": [
         {       "prefix": "2001:dead:beef:aa00::",
                 "prefix-len": 56,
                 "delegated-len": 57
         } ]
}


Thanks

Ede