Package: isc-dhcp-server Version: 4.3.5-3.1 Followup-For: Bug #712503 Dear Maintainer,
-- System Information: Debian Release: 9.4 APT prefers stable APT policy: (700, 'stable'), (650, 'testing'), (500, 'stable-updates') Architecture: amd64 (x86_64) Kernel: Linux 4.9.0-6-amd64 (SMP w/4 CPU cores) Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US:en (charmap=UTF-8) Shell: /bin/sh linked to /bin/dash Init: systemd (via /run/systemd/system) Actually, there are two issues: 1) dhcpd is listening on random port (UDP) for all interfaces, no configuration option or CLI switch can fix with this situation. 2) moreover, dhcpd is listening for UDPv6 too, even if you include -4 option for dhcpd (I have ipv6 disabled via sysctl) $ cat /etc/default/isc-dhcp-server INTERFACES="eth2" OPTIONS="-4" PID TTY STAT TIME COMMAND 7714 ? Ss 0:00 /usr/sbin/dhcpd -4 -q -cf /etc/dhcp/dhcpd.conf eth2 $ netstat -tulp udp 0 0 0.0.0.0:23961 0.0.0.0:* 7714/dhcpd udp6 0 0 :::64049 :::* 7714/dhcpd
