The listed Kea logs for DHCP_LEASE_ADVERT would indicate that Kea is sending an 
OFFER to the DISCOVER request.   It would seem unlikely that Kea logs the 
ADVERT without attempting to send the offer packet on the network (such a bug 
would likely affect more than your client).   You also mention that you had 
similar issue with the legacy ISC dhcpd server.   You also mention recent issue 
began after distro upgrade.  Assuming there were not changes to Kea with the 
upgrade.

Not enough info in thread to determine, but seems more probable that the OFFER 
is being dropped/blocked by your OS/network layer.  Generally, if offer packet 
is blocked by something such as NFTables/IPTables, Kea would also log something 
along the lines of "failed to send DHCPv4 packet: pkt4 send failed: sendmsg() 
returned with an error: Operation not permitted”.  Apparmor/SELinux or similar 
security controls could also be in play.

You may want to try packet capture without filters (or just limit to port 
67/68) in case there are some breadcrumbs there.  If you have not already, 
recommend checking OS logs as well in case response packet dropped by your 
host.  You can also turn up Kea loglevel (severity DEBUG and increased 
debuglevel) but since Kea is logging ADVERT, not sure you’ll learn more there.  
See https://kea.readthedocs.io/en/kea-2.4.1/arm/logging.html#logging-levels  



> On Jan 19, 2024, at 07:37, Gavin Davenport <gav...@gavdav.net> wrote:
> 
> Does anyone have any idea why dhcp would not actually emit the dhcp response 
> following logging
> 2024-01-19 13:35:02.390 INFO  [kea-dhcp4.leases/855.139674733151936] 
> DHCP4_LEASE_ADVERT [hwtype=1 fc:fe:c2:05:3e:b7], cid=[no info], 
> tid=0xf3db5a1f: lease 10.99.99.3 will be advertised
> 2024-01-19 13:35:17.539 INFO  [kea-dhcp4.leases/855.139674758330048] 
> DHCP4_LEASE_ADVERT [hwtype=1 fc:fe:c2:05:3e:b7], cid=[no info], 
> tid=0xf3db5a1f: lease 10.99.99.3 will be advertised
> 2024-01-19 13:35:32.689 INFO  [kea-dhcp4.leases/855.139674749937344] 
> DHCP4_LEASE_ADVERT [hwtype=1 fc:fe:c2:05:3e:b7], cid=[no info], 
> tid=0xf3db5a1f: lease 10.99.99.3 will be advertised
> 
> It's received the discover (visible in tcpdump) but why would it get jammed 
> and refuse to respond to this ?
> 
> is there anything I have misconfigured in the scope ? Are there any improved 
> debugging options I might use ?
> 
> -----Original Message-----
> From: Kea-users <kea-users-boun...@lists.isc.org> On Behalf Of Gavin Davenport
> Sent: 16 January 2024 20:46
> To: Kea user's list <kea-users@lists.isc.org>
> Subject: Re: [Kea-users] dhcp4 server stops responding to a device
> 
> I was using isc-dhcp and had this behaviour too:
> https://gitlab.isc.org/isc-projects/dhcp/-/issues/177
> 
> I switched to kea-dhcp4 and it fixed it.
> 
> I've since done a distro upgrade and it's gone flaky again. 
> 
> I've no idea how to diagnose signal quality from the data I can get from the 
> wiser (there's a rest endpoint) but this isn't available when it gets 
> unaddressed.

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