[Kea-users] New user, trying to use ip-reservations-unique feature

[Kevin P. Fleming]

FYI: I avoided this problem entirely by configuring a stable
'client-id' in NetworkManager on the laptops in question. They now get
the same address (via host reservation) regardless of the connection
method, and only a single reservation is required in Kea for each one.

On Sat, Jan 29, 2022 at 9:46 AM Kevin P. Fleming <kevin at km6g.us> wrote:
>
> Hello there! I've just deployed Kea 2.0.1 (using the ISC packages) on
> a pair of machines in my network to provide HA DHCP4/DHCP6 services
> (replacing the ISC DHCPd-based service in my layer 3 switches, which
> don't provide sufficient functionality for my needs).
>
> I've got the daemons running and HA mode working; most DHCP4
> functionality is working fine.
>
> However, one feature of Kea DHCP that I'd like to use is 'multiple
> reservations for the same IP address', which was enabled when the
> 'ip-reservations-unique' configuration option was added. In my case I
> have laptops with both WiFi and Ethernet connections, with different
> MAC addresses, but I want them to have the same IP addresses
> regardless of the connection mode. They will never be connected via
> both interfaces at once, in fact the laptop BIOSes have been
> configured to 'rfkill' the WiFi interfaces when the Ethernet
> interfaces are connected.
>
> I've posted a copy of my configuration here: https://km6g.us/kea-dhcp4.conf
>
> If you take a look at subnet4 id '88', you'll see two reservations for
> 'balrog22' with the same IP address but different MAC addresses. While
> the DHCP4 server accepts this configuration, when the laptop attempts
> to obtain an address the server logs a message complaining about the
> duplication:
>
> Jan 29 09:39:10 edge21-b kea-dhcp4[725279]: WARN
> ALLOC_ENGINE_V4_DISCOVER_ADDRESS_CONFLICT [hwtype=1
> a8:64:f1:30:88:0b], cid=[01:a8:64:f1:30:88:0b], tid=0xcf6b412e:
> conflicting reservation for address 192.168.88.192 with existing lease
> Address:       192.168.88.192
> Jan 29 09:39:10 edge21-b kea-dhcp4[725279]: Valid life:    86400
> Jan 29 09:39:10 edge21-b kea-dhcp4[725279]: Cltt:          1643462468
> Jan 29 09:39:10 edge21-b kea-dhcp4[725279]: Hardware addr: 90:2e:16:d6:a4:1e
> Jan 29 09:39:10 edge21-b kea-dhcp4[725279]: Client id:     (none)
> Jan 29 09:39:10 edge21-b kea-dhcp4[725279]: Subnet ID:     88
> Jan 29 09:39:10 edge21-b kea-dhcp4[725279]: State:         default
> Jan 29 09:39:10 edge21-b kea-dhcp4[725279]: INFO  DHCP4_LEASE_ADVERT
> [hwtype=1 a8:64:f1:30:88:0b], cid=[01:a8:64:f1:30:88:0b],
> tid=0xcf6b412e: lease 192.168.88.128 will be advertised
> Jan 29 09:39:10 edge21-b kea-dhcp4[725279]: INFO  DHCP4_LEASE_ALLOC
> [hwtype=1 a8:64:f1:30:88:0b], cid=[01:a8:64:f1:30:88:0b],
> tid=0xcf6b412e: lease 192.168.88.128 has been allocated for 86400
> seconds
>
> Have I overlooked something in the configuration, or am I trying to
> use this feature in a way that it is not expected to operate?