[Kea-users] DHCPOFFER not sent

[Sneaky]

Hi,

I'm tinkering in my home network migrating services from one Pi to 
another. On the old Pi I'm running ISC DHCP to handle client configuration.

I stumbled upon Kea DHCP and thought I give that a try on the new Pi. I 
migrated the ISC configuration and adjusted it where needed. However, 
for some, as yet mysterious reason, Kea does not send any outgoing packages.

I have the ISC Pi, which is in the same subnet as the Kea Pi, configured 
with "deny all clients" in the pool configuration. That pool is 
configured and enabled on the Kea Pi now. Here is what I see in the logs:

1. DHCPREQUEST for 192.168.201.162
2. DHCPNAK on 192.168.201.162 (ISC Pi)
3. DHCPDISCOVER from ... no free leases (ISC Pi)
4. DHCP4_LEASE_ADVERT ... lease 192.168.201.151 will be advertised (Kea Pi)

That's it. On the ISC Pi the DHSCPDISCOVER message repeats as the client 
attempts to acquire a lease as does the DHCP4_LEASE_ADVERT on Kea Pi.

I tried to rule out common culprits and turned off the firewall 
(firewalld, nftables) on Kea Pi. I also tried with SELinux in permissive 
mode to no avail.

On both sides DHCP listens on a VLAN interface (eht0.201).

With full debug logging enabled in kea-dhcp4.conf I can see that Kea is 
taking all the necessary steps up to:

DEBUG DHCP4_RESPONSE_DATA [hwtype=1 00:26:22:b6:31:ea], cid=[no info], 
tid=0x3394317c: responding with packet DHCPOFFER (type 2), packet 
details: local_address=192.168.201.242:67, 
remote_address=192.168.201.151:68, msg_type=DHCPOFFER (2), 
transid=0x3394317c,
options:
   type=001, len=004: 4294967040 (uint32)
   type=003, len=004: 192.168.201.242
   type=006, len=004: 192.168.201.242
   type=012, len=021: "slaptop.penguinpee.nl" (string)
   type=015, len=013: "penguinpee.nl" (string)
   type=028, len=004: 192.168.201.255 (ipv4-address)
   type=051, len=004: 21600 (uint32)
   type=053, len=001: 2 (uint8)
   type=054, len=004: 192.168.201.242
   type=058, len=004: 900 (uint32)
   type=059, len=004: 1800 (uint32)

But the offer is never sent. I snooped on another machine in the same 
subnet, but could only capture the packages from client and ISC Pi.

I'm running Kea DHCP 2.0.2. The ISC Pi is running Raspbian 9 (stretch), 
while the Kea Pi is running Fedora Linux 35 (Server Edition).

Any help/pointers as to what else to examine are very much appreciated.

Thanks,

Sandro