diff -Nru isc-dhcp-4.3.3/debian/changelog isc-dhcp-4.3.3/debian/changelog
--- isc-dhcp-4.3.3/debian/changelog	2016-11-04 16:57:07.000000000 +0000
+++ isc-dhcp-4.3.3/debian/changelog	2016-12-09 17:45:11.000000000 +0000
@@ -1,3 +1,11 @@
+isc-dhcp (4.3.3-5ubuntu12.6) xenial; urgency=medium
+
+  * debian/initramfs/lib/etc/dhcp/dhclient-enter-hooks.d/config: clean up
+    script to remove IPv4 bits that would never be called; since for this SRU
+    we only do IPv6. (LP: #1621507)
+
+ -- Mathieu Trudel-Lapierre <cyphermox@ubuntu.com>  Thu, 08 Dec 2016 17:43:34 +0100
+
 isc-dhcp (4.3.3-5ubuntu12.5) xenial; urgency=medium
 
   * debian/initramfs/lib/etc/dhcp/dhclient-enter-hooks.d/config: fix script to
diff -Nru isc-dhcp-4.3.3/debian/initramfs-tools/lib/etc/dhcp/dhclient-enter-hooks.d/config isc-dhcp-4.3.3/debian/initramfs-tools/lib/etc/dhcp/dhclient-enter-hooks.d/config
--- isc-dhcp-4.3.3/debian/initramfs-tools/lib/etc/dhcp/dhclient-enter-hooks.d/config	2016-11-04 16:57:07.000000000 +0000
+++ isc-dhcp-4.3.3/debian/initramfs-tools/lib/etc/dhcp/dhclient-enter-hooks.d/config	2016-12-09 17:45:11.000000000 +0000
@@ -1,38 +1,13 @@
 #!/bin/sh
 
-IPVER=""
-if echo "$reason" | grep -q '6$'; then
-	IPVER=6
-fi
-
 case "$reason" in
-BOUND)
-	echo "DEVICE=$interface" >> /run/net-$interface.conf
-	echo "PROTO=dhcp" >> /run/net-$interface.conf
-	echo "IPV4PROTO=dhcp" >> /run/net-$interface.conf
-	echo "IPV4ADDR=$new_ip_address" >> /run/net-$interface.conf
-	echo "IPV4NETMASK=$new_subnet_mask" >> /run/net-$interface.conf
-	echo "IPV4BROADCAST=$new_broadcast_address" >> /run/net-$interface.conf
-	echo "IPV4GATEWAY=$new_routers" >> /run/net-$interface.conf
-	echo "IPV4DNS0=$new_domain_name_servers" >> /run/net-$interface.conf
-	echo "ROOTSERVER=$new_routers" >> /run/net-$interface.conf
-	if [ -n "$host_name"]; then
-		echo "HOSTNAME=$new_host_name" >> /run/net-$interface.conf
-	fi
-	if [ -n "$domain_name"]; then
-		echo "DNSDOMAIN=$new_domain_name" >> /run/net-$interface.conf
-	fi
-	if [ -n "$new_domain_search"]; then
-		echo "DOMAINSEARCH=$new_domain_search" >> /run/net-$interface.conf
-	fi
-	;;
 BOUND6)
-	echo "DEVICE6=$interface" >> /run/net6-$interface.conf
+	echo "DEVICE6=$interface" > /run/net6-$interface.conf
 	echo "IPV6PROTO=dhcp6" >> /run/net6-$interface.conf
 	echo "IPV6ADDR=$new_ip6_address" >> /run/net6-$interface.conf
 	echo "IPV6NETMASK=$new_ip6_prefixlen" >> /run/net6-$interface.conf
 	echo "IPV6DNS0=$new_dhcp6_name_servers" >> /run/net6-$interface.conf
-	if [ -n "$new_dhcp6_domain_search"]; then
+	if [ -n "$new_dhcp6_domain_search" ]; then
 		echo "IPV6DOMAINSEARCH=$new_dhcp6_domain_search" >> /run/net6-$interface.conf
 	fi
 	;;