Comment 66 for bug 1176046

[Verification Xenial]

{Before upgrade}
===
ii isc-dhcp-client 4.2.4-7ubuntu12.10 amd64 ISC DHCP client
ii isc-dhcp-client-noddns 4.2.4-7ubuntu12.10 amd64 Dynamic DNS (DDNS) disabled DHCP client
ii isc-dhcp-common 4.2.4-7ubuntu12.10 amd64 common files used by all the isc-dhcp* packages

# netstat -anputa | grep -i dhclient
udp 0 0 0.0.0.0:68 0.0.0.0:* 1686/dhclient

# ls -altr /sbin/dhclient*
-rwxr-xr-x 1 root root 7545313 May 25 12:30 /sbin/dhclient
-rwxr-xr-x 1 root root 15286 May 25 12:32 /sbin/dhclient-script
-rwxr-xr-x 1 root root 1668160 May 25 12:32 /sbin/dhclient-ddns

# more /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04.5 LTS"

{After upgrade}
===
ii isc-dhcp-client 4.3.3-5ubuntu12.7 amd64 DHCP client for automatically obtaining an IP address

# netstat -anputa | grep -i dhclient
udp 0 0 0.0.0.0:68 0.0.0.0:* 150/dhclient

^^ expected result since Xenial does the opposite :
isc-dhcp-client : with random extra ports
isc-dhcp-client-ddns : with random extra ports

Basically, Xenial users has to install "isc-dhcp-client-ddns" if they want the DDNS functionality.

# dist-upgrade/history.log
Remove: libxapian22:amd64 (1.2.16-2ubuntu1), ==> isc-dhcp-client-noddns:amd64 (4.2.4-7ubuntu12.10) <==, systemd-services:amd64 (204-5ubuntu20.24), python3.4:amd64 (3.4.3-1ubuntu1~14.04.5), python3.4-minimal:amd64 (3.4.3-1ubuntu1~14.04.5), libpython3.4-stdlib:amd64 (3.4.3-1ubuntu1~14.04.5), libpython3.4-minimal:amd64 (3.4.3-1ubuntu1~14.04.5), perl-modules:amd64 (5.18.2-2ubuntu1.1), aptitude:amd64 (0.6.8.2-1ubuntu4), libasprintf0c2:amd64 (0.18.3.1-1ubuntu3)
End-Date: 2017-05-29 11:00:57

Package has been removed :
rc isc-dhcp-client-noddns 4.2.4-7ubuntu12.10 amd64 Dynamic DNS (DDNS) disabled DHCP client

The upgrade does remove if installed "isc-dhcp-client-noddns" and replaces it by "isc-dhcp-client".