diff -Nru isc-dhcp-4.3.5/debian/changelog isc-dhcp-4.3.5/debian/changelog
--- isc-dhcp-4.3.5/debian/changelog	2017-01-19 12:11:21.000000000 -0500
+++ isc-dhcp-4.3.5/debian/changelog	2017-06-07 16:38:45.000000000 -0400
@@ -1,3 +1,12 @@
+isc-dhcp (4.3.5-3ubuntu2) artful; urgency=medium
+
+  * Strip interface alias extension from interface names provided to
+    dhclient; all enumerated interface names also have their alias
+    extension stripped.  Without this, DHCPv6 fails for interface aliases.
+    (LP: #1693819)
+
+ -- Dan Streetman <dan.streetman@canonical.com>  Wed, 07 Jun 2017 16:38:45 -0400
+
 isc-dhcp (4.3.5-3ubuntu1) zesty; urgency=low
 
   * Merge from Debian unstable.  Remaining changes:
diff -Nru isc-dhcp-4.3.5/debian/patches/series isc-dhcp-4.3.5/debian/patches/series
--- isc-dhcp-4.3.5/debian/patches/series	2017-01-19 12:11:21.000000000 -0500
+++ isc-dhcp-4.3.5/debian/patches/series	2017-06-07 16:38:38.000000000 -0400
@@ -32,3 +32,4 @@
 dhcp-improved-xid-correct-byte-order.patch
 dhcp-4.2.4-dhclient-options-changed.patch
 ubuntu-dhcpd-conf.patch
+strip-interface-alias.patch
diff -Nru isc-dhcp-4.3.5/debian/patches/strip-interface-alias.patch isc-dhcp-4.3.5/debian/patches/strip-interface-alias.patch
--- isc-dhcp-4.3.5/debian/patches/strip-interface-alias.patch	1969-12-31 19:00:00.000000000 -0500
+++ isc-dhcp-4.3.5/debian/patches/strip-interface-alias.patch	2017-06-07 16:38:38.000000000 -0400
@@ -0,0 +1,39 @@
+Author: Dan Streetman <dan.streetman@canonical.com>
+Description: Since isc-dhcp strips the interface alias from all
+  interfaces it enumerates, when comparing the cmdline interface
+  name to find the matching enumerated interface, the cmdline name
+  must have its alias stripped also.  Without this, DHCPv6 fails
+  when using an interface alias.
+Forwarded: yes
+Bug: [ISC bug tracking is private; bug email has been sent]
+Bug-Ubuntu: https://bugs.launchpad.net/ubuntu/+source/isc-dhcp/+bug/1693819
+
+
+Index: isc-dhcp-4.3.5/client/dhclient.c
+===================================================================
+--- isc-dhcp-4.3.5.orig/client/dhclient.c
++++ isc-dhcp-4.3.5/client/dhclient.c
+@@ -447,15 +447,19 @@ main(int argc, char **argv) {
+ 			      " requested interface %s", argv[i]);
+ 		} else {
+ 		    struct interface_info *tmp = NULL;
++		    int len;
+ 
+ 		    status = interface_allocate(&tmp, MDL);
+ 		    if (status != ISC_R_SUCCESS)
+ 			log_fatal("Can't record interface %s:%s",
+ 				  argv[i], isc_result_totext(status));
+-		    if (strlen(argv[i]) >= sizeof(tmp->name))
+-			    log_fatal("%s: interface name too long (is %ld)",
+-				      argv[i], (long)strlen(argv[i]));
+-		    strcpy(tmp->name, argv[i]);
++		    /* strip any interface alias, e.g. eth1:1 -> eth1 */
++		    len = strchrnul(argv[i], ':') - argv[i];
++		    if (len >= sizeof(tmp->name))
++			    log_fatal("%s: interface name too long (is %d)",
++				      argv[i], len);
++		    strncpy(tmp->name, argv[i], len);
++		    tmp->name[len] = 0;
+ 		    if (interfaces) {
+ 			    interface_reference(&tmp->next,
+ 						interfaces, MDL);