diff --git a/releasenotes/notes/fix-ipv6-route-exists-b5f07569270b6066.yaml b/releasenotes/notes/fix-ipv6-route-exists-b5f07569270b6066.yaml
new file mode 100644
index 0000000000..858dd799eb
--- /dev/null
+++ b/releasenotes/notes/fix-ipv6-route-exists-b5f07569270b6066.yaml
@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fix a bug where docker daemon occasionally returns error:
+    `failed to set IPv6 gateway while updating gateway: file exists: unknown`
+    when network_isolation is enabled.
\ No newline at end of file
diff --git a/trove/taskmanager/models.py b/trove/taskmanager/models.py
index c76166a793..c0f437646a 100755
--- a/trove/taskmanager/models.py
+++ b/trove/taskmanager/models.py
@@ -583,11 +583,16 @@ class FreshInstanceTasks(FreshInstance, NotifyMixin, ConfigurationMixin):
                 nic_info["ipv4_cidr"] = subnet.get("cidr")
                 nic_info["ipv4_gateway"] = subnet.get("gateway_ip")
                 nic_info["ipv4_host_routes"] = subnet.get("host_routes")
+            # NOTE: only if the ipv6_ra_mode is dhcpv6-stateful,
+            # we need to configure the ip route for container. for slaac
+            # and dhcpv6-stateless mode, the route will be configured
+            # by the nic itself via the RA protocol.
             elif subnet.get("ip_version") == 6:
                 nic_info["ipv6_address"] = fixed_ip.get("ip_address")
                 nic_info["ipv6_cidr"] = subnet.get("cidr")
-                nic_info["ipv6_gateway"] = subnet.get("gateway_ip")
                 nic_info["ipv6_host_routes"] = subnet.get("host_routes")
+                if subnet.get("ipv6_ra_mode") == "dhcpv6-stateful":
+                    nic_info["ipv6_gateway"] = subnet.get("gateway_ip")
         return nic_info
 
     def create_instance(self, flavor, image_id, databases, users,