I would like my isc-dhcp-server instance to listen on my LAN interface only because I'm investigating an issue with my "WiFi router" and configured INTERFACES='p18p1' in /etc/default/isc-dhcp-server where p18p1 is my LAN interface. However, after restart with sudo systemctl restart isc-dhcp-server.service if see

udp        0      0    *                           23088/dhcpd         

in the output of sudo netstat -tupln | grep 67 which leads me to believe that the interfaces configuration value is ignored. Specifying interfaces p18p1; in /etc/dhcpd/dhcpd.conf causes the systemd unit to fail to start - it seems to enforce specification of interfaces in /etc/default/isc-dhcp-server.

I'm using Ubuntu 17.04.

  • Whats the output of systemctl cat isc-dhcp-server.service? Also if you do sudo /etc/init.d/isc-dhcp-server restart, does it work? – heemayl May 9 '17 at 3:16

Try seting the INTERFACE variable in /etc/default/isc-dhcp-server to the desired interface. For example:


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