[Kea-users] subclass handling in kea-dhcp

[Darren Ankney]

“subclass” in ISC DHCP was a “speed hack” according to the manual pages.

Basically, you are going to want to create a class called “denyClients” adding the macs that you want to deny to the class (https://kea.readthedocs.io/en/kea-2.2.0/arm/classify.html) possibly something like the below:

“client-classes”: [
  {
    “name”: “denyClients”,
    “test”: “hex string(pkt4.mac, ‘:’) == '11:22:33:44:ab:66’  or hex string(pkt4.mac, ‘:’) == '11:22:33:43:ab:66’ or hex string(pkt4.mac, ‘:’) == '11:22:33:42:ab:66’ ”
  },

Tho the test line may not be quite right as I’ve not tested the hex string(pkt4.mac, ‘:’) to make sure that works like I think it does (https://kea.readthedocs.io/en/kea-2.2.0/arm/classify.html#hexstring).

Then (there might be a better way to do this) define a class that tests membership based on the client not being a member of denyClients

  {
    “name”: “allowClients”,
    “test”: "(not(member(‘denyClients')))”
 }
]

Then in the subnet add a require class in your pools statement:
"pools": [
  {
    "pool": “1.2.3.0-1.2.3.254",
    "client-class": "allowClients"





> On Dec 14, 2022, at 9:30 AM, Kraishak Mahtha <kraishak.edu at gmail.com> wrote:
> 
> Hi All, 
> 
> I am looking for the equivalent option of ISC dhcp subclass in kea-dhcp4 but I couldn't find any, I have a case where I need to decline dhcp-lease grants to given specific mac addresses so trying to match the same in kea-version but I  couldn't find any sub-class equivalent, can we add the specific data (here mac address as the members of the specific class) in kea
> 
> MY ISC DHCP config
> class "denyClients" {
>          match substring (hardware, 1, 6);
>          deny booting;
> }
> subclass "denyClients" 11:22:33:44:ab:66;
> subclass "denyClients" 11:22:33:43:ab:66;
> subclass "denyClients" 11:22:33:42:ab:66;
> subnet 12.0.0.0 netmask 255.255.255.0 {
> pool {
> failover peer "Test";
> range 12.0.0.2 12.0.0.2;
> deny members of "denyClients";
> }
> default-lease-time 3600;
>  option routers 12.0.0.1;
>  option subnet-mask 255.255.255.0;
> }
> 
> 
> Can anyone please advise or suggest how to add members to the DHCP class or the data for which the class should be applied
> 
> Thanks in Advance
> Kraishak
> 
> 
> 
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