[Kea-users] Need help assigning subnets by class with host reservations

mrobti at insiberia.net mrobti at insiberia.net
Wed Nov 9 19:28:52 UTC 2016

On 2016-11-09 07:56, Thomas Markwalder wrote:
> On 11/9/16 4:20 AM, mrobti at insiberia.net wrote:
>> On 2016-11-08 15:44, mrobti at insiberia.net wrote:
>>> I want to assign a client-class using hwaddr, from MySQL backend, and
>>> restrict a subnet for that client-class. In other words, only allow
>>> clients with known MAC addresses to use the subnet they are trying to
>>> connect to.
>>> DB hosts table has an entry for the client:
>>> dhcp4_subnet_id = 1
>>> dhcp_identifier_type = 0
>>> dhcp_identifier = UNHEX(REPLACE('aa:bb:cc:dd:ee:ff', ':', ''))
>>> hostname = test.local
>>> dhcp4_client_classes = test_class
>>> Config file has:
>>> "client-classes": [ {
>>>   "name": "test_class"
>>> } ],
>>> "subnet4": [ {
>>>   "id": 1,
>>>   "subnet": "",
>>>   "pools": [ { "pool": " -" } ],
>>>   "client-class": "test_class"
>>> } ],
>>> But Kea says (debug level 50):
>>> : client packet has been assigned to the following class(es):
>>> : failed to select subnet for the client
>>> : no suitable subnet configured for a direct client
>>> It works if I remove "client-class" from the subnet definition, so
>>> something is not synchronizing the class somewhere.
>>> Could it be a problem that the DB hosts entry has no ipv4_address
>>> listed? (that column is NULL)  I don't have any other ideas.
>> I've found this in the logs:
>> : HOSTS_CFG_GET_ALL_IDENTIFIER get all hosts with reservations using
>> identifier: hwaddr=aa:bb:cc:dd:ee:ff
>> hwaddr=aa:bb:cc:dd:ee:ff, found 0 host(s)
>> Why would this happen? Yes, I double checked the MAC address. I
>> enabled MySQL logging, and I can't match up timestamps exactly, but I
>> do find a query:
>> SELECT host_id, dhcp_identifier, dhcp_identifier_type,
>> dhcp4_subnet_id, dhcp6_subnet_id, ipv4_address, hostname,
>> dhcp4_client_classes, dhcp6_client_classes FROM hosts WHERE
>> dhcp4_subnet_id = ? AND dhcp_identifier_type = ?    AND
>> dhcp_identifier = ?
>> I don't know if it's possible to see the executed version of this
>> prepared query(?). Is it possible that the value Kea is placing in the
>> query is not the correct binary string?
>> _______________________________________________
>> Kea-users mailing list
>> Kea-users at lists.isc.org
>> https://lists.isc.org/mailman/listinfo/kea-users
> Hello:
> We are looking into this for you.  As you probably know,  Kea will look
> first for hosts defined its configuration file and then within the 
> hosts
> database (if it is specified).  Any log statements you see that contain
> "HOSTS_CFG_" pertain to looking at hosts defined via the configuration
> file.  In your case, since there are none, you see none found.  When 
> Kea
> accesses the host database the logs should contain
> HOSTS_MGR_ALTERNATIVE_.   The following is a snippet from of the log in
> a setup I am testing with:
> 2016-11-09 10:18:45.018 DEBUG [kea-dhcp4.hosts/24940]
> HOSTS_CFG_GET_ONE_SUBNET_ID_ADDRESS4 get one host with reservation for
> subnet id 1 and IPv4 address
> 2016-11-09 10:18:45.018 DEBUG [kea-dhcp4.hosts/24940]
> HOSTS_CFG_GET_ALL_ADDRESS4 get all hosts with reservations for IPv4
> address
> 2016-11-09 10:18:45.018 DEBUG [kea-dhcp4.hosts/24940]
> HOSTS_CFG_GET_ALL_ADDRESS4_COUNT using address, found 0 
> host(s)
> 2016-11-09 10:18:45.018 DEBUG [kea-dhcp4.hosts/24940]
> HOSTS_CFG_GET_ONE_SUBNET_ID_ADDRESS4_NULL host not found using subnet 
> id
> 1 and address
> 2016-11-09 10:18:45.018 DEBUG [kea-dhcp4.hosts/24940]
> HOSTS_MGR_ALTERNATE_GET4_SUBNET_ID_ADDRESS4 trying alternate source for
> host using subnet id 1 and address
> The last log statement indicates that Kea is looking in MySQL for hosts
> that have the allocated address.  It just so happens that Kea actually
> conducted a search in MySQL prior to the last one show above.  This
> search is done by subnet id and dhcp identifier.   However the function
> that performs this search happens to be missing a log entry.  This is
> why you see  the two selects  you cited in the MySQL log but only one
> log message against the alternate.   The original function we used
> was deprecated without the new one getting a log message.  Sorry about
> that.
> On the surface, it looks like Kea should be matching your host, we're
> still researching it.  You might try defining your host in the
> configuration file, for testing purposes.   Do you have a packet 
> capture
> and what version of Kea are you running?

Thank you for your response. I don't have a packet capture at the 
moment, but I do see the HOSTS_MGR_ALTERNATE_ line just like yours. I'm 
running the ubuntu package which shows version 1.0.0, the package name 
is version 1.0.0-1build1. I know that's behind the curve, but sometimes 
don't these packages include bugfixes from newer versions than they 

I can begrudgingly compile from source, but would not be happy taking it 
outside the system package manager.

I just tried to test by putting the host in the config file, got this 
startup error:
DHCP4_PARSER_FAIL failed to create or run parser for configuration 
element subnet4: unsupported configuration parameter 'client-classes'

Looks like assigning client-classes to host reservations was a feature 
only added after version 1.0? Can you please confirm when it was added?

More information about the Kea-users mailing list