isc-dhcp-server ignoring requests because there are no IPv4 addresses configured

[Markus Krainz]

Hi,

not sure if this is the right place to ask. I recently installed
isc-dhcp-server on a new computer. This computer runs Armbian 22.11.4 Jammy
based on Ubuntu 22.04.1 LTS.
The isc-dhcp-server package version is 4.4.1-2.3ubuntu2.3.

My  /etc/default/isc-dhcp-server contains:
INTERFACESv4="eth0"

However on some boots, systemd fails to start the isc-dhcp-server service.
Checking the logs I found:

Feb 02 09:36:02 rock64 sh[1162]: No subnet declaration for eth0 (no IPv4
addresses).
Feb 02 09:36:02 rock64 sh[1162]: ** Ignoring requests on eth0.  If this is
not what
Feb 02 09:36:02 rock64 sh[1162]:    you want, please write a subnet
declaration
Feb 02 09:36:02 rock64 sh[1162]:    in your dhcpd.conf file for the network
segment
Feb 02 09:36:02 rock64 sh[1162]:    to which interface eth0 is attached. **
Feb 02 09:36:02 rock64 sh[1162]: Not configured to listen on any interfaces!
Feb 02 09:36:02 rock64 sh[1162]: If you think you have received this
message due to a bug rather
Feb 02 09:36:02 rock64 sh[1162]: than a configuration issue please read the
section on submitting
Feb 02 09:36:02 rock64 sh[1162]: bugs on either our web page at www.isc.org
or in the README file
Feb 02 09:36:02 rock64 dhcpd[1162]: No subnet declaration for eth0 (no IPv4
addresses).
Feb 02 09:36:02 rock64 sh[1162]: before submitting a bug.  These pages
explain the proper
Feb 02 09:36:02 rock64 sh[1162]: process and the information we find
helpful for debugging.
Feb 02 09:36:02 rock64 sh[1162]: exiting.
Feb 02 09:36:02 rock64 dhcpd[1162]: ** Ignoring requests on eth0.  If this
is not what
Feb 02 09:36:02 rock64 dhcpd[1162]:    you want, please write a subnet
declaration
Feb 02 09:36:02 rock64 dhcpd[1162]:    in your dhcpd.conf file for the
network segment
Feb 02 09:36:02 rock64 dhcpd[1162]:    to which interface eth0 is attached.
**
Feb 02 09:36:02 rock64 dhcpd[1162]:
Feb 02 09:36:02 rock64 dhcpd[1162]:
Feb 02 09:36:02 rock64 dhcpd[1162]: Not configured to listen on any
interfaces!
Feb 02 09:36:02 rock64 dhcpd[1162]:
Feb 02 09:36:02 rock64 dhcpd[1162]: If you think you have received this
message due to a bug rather
Feb 02 09:36:02 rock64 dhcpd[1162]: than a configuration issue please read
the section on submitting
Feb 02 09:36:02 rock64 dhcpd[1162]: bugs on either our web page at
www.isc.org or in the README file
Feb 02 09:36:02 rock64 dhcpd[1162]: before submitting a bug.  These pages
explain the proper
Feb 02 09:36:02 rock64 dhcpd[1162]: process and the information we find
helpful for debugging.
Feb 02 09:36:02 rock64 dhcpd[1162]:
Feb 02 09:36:02 rock64 systemd[1]: isc-dhcp-server.service: Main process
exited, code=exited, status=1/FAILURE
Feb 02 09:36:02 rock64 dhcpd[1162]: exiting.
Feb 02 09:36:02 rock64 systemd[1]: isc-dhcp-server.service: Failed with
result 'exit-code'.


However when I check the interfaces right after boot:

rock64:markus:# ip address
1: lo: [....]
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group
default qlen 1000
    link/ether c2:48:08:12:53:18 brd ff:ff:ff:ff:ff:ff
    inet 192.168.129.22/24 brd 192.168.129.255 scope global noprefixroute
eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::c048:8ff:fe12:5318/64 scope link
       valid_lft forever preferred_lft forever


I have an ip address and subnet successfully statically set via my applied
netplan (renderer: NetworkManager).

I double checked that network-online is a dependency for isc-dhcp-server so
it doesn't try to start before the IP address is configured, but
network-online is correctly already a dependency by default:

rock64:markus:# systemctl list-dependencies isc-dhcp-server
isc-dhcp-server.service
● ├─-.mount
● ├─system.slice
● ├─network-online.target
● │ └─networking.service
● └─sysinit.target [...]


Any idea what could be the problem?

Best regards
Markus
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