diff -Nru neutron-16.4.0/debian/changelog neutron-16.4.0/debian/changelog
--- neutron-16.4.0/debian/changelog	2021-07-28 23:20:43.000000000 +0200
+++ neutron-16.4.0/debian/changelog	2021-09-14 18:25:11.000000000 +0200
@@ -1,3 +1,9 @@
+neutron (2:16.4.0-0ubuntu4) focal; urgency=medium
+
+  * Trivial: check if ipv6 is available for IptablesManager (LP: 1915480).
+
+ -- Alin-Gabriel Serdean <alin.serdean@canonical.com>  Tue, 14 Sep 2021 18:25:11 +0200
+
 neutron (2:16.4.0-0ubuntu3) focal; urgency=medium
 
   * d/p/revert-l3-ha-retry-when-setting-ha-router-gw-status.patch: Revert
diff -Nru neutron-16.4.0/debian/patches/b6a6065.diff neutron-16.4.0/debian/patches/b6a6065.diff
--- neutron-16.4.0/debian/patches/b6a6065.diff	1970-01-01 01:00:00.000000000 +0100
+++ neutron-16.4.0/debian/patches/b6a6065.diff	2021-09-14 18:25:11.000000000 +0200
@@ -0,0 +1,55 @@
+From b6a6065f9f90f83f80e3a3a997bf382b38763b29 Mon Sep 17 00:00:00 2001
+From: Alin-Gabriel Serdean <alin.serdean@canonical.com>
+Date: Fri, 13 Aug 2021 11:13:20 +0300
+Subject: [PATCH] Trivial: check if ipv6 is available for IptablesManager
+
+Conflicts:
+	neutron/agent/ovn/metadata/agent.py
+
+To resolve conflict, rearrange alphabetically the imports from
+oslo_utils.
+
+Change-Id: I3caf131041a852671a556b064c641fe34f8f5ed0
+Closes-Bug: #1915480
+(cherry picked from commit 6cf71cbd6a71b4849470874379877c7ca2a8fc25)
+---
+
+diff --git a/neutron/agent/linux/dhcp.py b/neutron/agent/linux/dhcp.py
+index 96aab3b..d947518 100644
+--- a/neutron/agent/linux/dhcp.py
++++ b/neutron/agent/linux/dhcp.py
+@@ -1799,9 +1799,9 @@
+ 
+     def fill_dhcp_udp_checksums(self, namespace):
+         """Ensure DHCP reply packets always have correct UDP checksums."""
+-        iptables_mgr = iptables_manager.IptablesManager(use_ipv6=True,
+-                                                        nat=False,
+-                                                        namespace=namespace)
++        iptables_mgr = iptables_manager.IptablesManager(
++            use_ipv6=netutils.is_ipv6_enabled(), nat=False,
++            namespace=namespace)
+         ipv4_rule = ('-p udp -m udp --dport %d -j CHECKSUM --checksum-fill'
+                      % constants.DHCP_RESPONSE_PORT)
+         ipv6_rule = ('-p udp -m udp --dport %d -j CHECKSUM --checksum-fill'
+diff --git a/neutron/agent/ovn/metadata/agent.py b/neutron/agent/ovn/metadata/agent.py
+index 2fa8e2d..0dda323 100644
+--- a/neutron/agent/ovn/metadata/agent.py
++++ b/neutron/agent/ovn/metadata/agent.py
+@@ -18,6 +18,7 @@
+ from neutron_lib import constants as n_const
+ from oslo_concurrency import lockutils
+ from oslo_log import log
++from oslo_utils import netutils
+ from oslo_utils import uuidutils
+ from ovsdbapp.backend.ovs_idl import event as row_event
+ from ovsdbapp.backend.ovs_idl import vlog
+@@ -372,7 +373,8 @@
+             return
+ 
+         iptables_mgr = iptables_manager.IptablesManager(
+-            use_ipv6=True, nat=False, namespace=namespace, external_lock=False)
++            use_ipv6=netutils.is_ipv6_enabled(), nat=False,
++            namespace=namespace, external_lock=False)
+         rule = '-p tcp -m tcp -j CHECKSUM --checksum-fill'
+         iptables_mgr.ipv4['mangle'].add_rule('POSTROUTING', rule, wrap=False)
+         iptables_mgr.apply()