Comment 2 for bug 1818566

I still did write this patch :

[root@overcloud-controller-0 linux]# git diff
diff --git a/agent/linux/dhcp.py b/agent/linux/dhcp.py
index aa9f2cd..2cc00f1 100644
--- a/agent/linux/dhcp.py
+++ b/agent/linux/dhcp.py
@@ -21,6 +21,7 @@ import shutil
 import time

 import netaddr
+from neutron.common import ipv6_utils
 from neutron_lib import constants
 from neutron_lib import exceptions
 from oslo_config import cfg
@@ -1437,8 +1438,10 @@ class DeviceManager(object):
         # and added back statically in the call to init_l3() below.
         if network.namespace:
             ip_lib.IPWrapper().ensure_namespace(network.namespace)
- self.driver.configure_ipv6_ra(network.namespace, 'default',
- n_const.ACCEPT_RA_DISABLED)
+ self.use_ipv6 = ipv6_utils.is_enabled()
+ if self.use_ipv6:
+ self.driver.configure_ipv6_ra(network.namespace, 'default',
+ n_const.ACCEPT_RA_DISABLED)

         if ip_lib.ensure_device_is_ready(interface_name,
                                          namespace=network.namespace):