Comment 9 for bug 1176046

Sound similar to debian bug : https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=712503

The situation doesn't occur on Xenial (16.04 LTS), but present in Trusty (14.04) as a fix has been first introduce in Ubuntu with version : isc-dhcp (4.3.3-2)

Trusty :
#netstat -tulp | grep -i dhclient
udp 0 0 *:bootpc *:* 23402/dhclient
udp 0 0 *:bootpc *:* 1589/dhclient
udp 0 0 *:33749 *:* 1589/dhclient
udp 0 0 *:11662 *:* 23402/dhclient
udp6 0 0 [::]:7082 [::]:* 1589/dhclient
udp6 0 0 [::]:12668 [::]:* 23402/dhclient

Xenial:
# netstat -tulp | grep -i dhclient
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
udp 0 0 *:bootpc *:* 142/dhclient

# changelog
isc-dhcp (4.3.3-2) unstable; urgency=medium
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 ===> * Disable NSUPDATE (closes: #712503). <==
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