diff --git a/gestion/ipt.py b/gestion/ipt.py
index 70ca4d7c..37c0a1c9 100644
--- a/gestion/ipt.py
+++ b/gestion/ipt.py
@@ -30,6 +30,7 @@ from iptools import AddrInNet
 from ridtools import Rid, find_rid_plage
 import subprocess
 import netaddr
+import ip6tools
 
 blacklist_sanctions_ipv6 = list(blacklist_sanctions)
 blacklist_sanctions_ipv6.extend(blacklist_sanctions_soft)
@@ -126,6 +127,8 @@ class Ip6tables(object):
 
     def macip(self, mac, type_m):
         '''Fait la correspondance MAC-IP'''
+        if '<automatique>' == mac:
+            return
         tab = {'serveurs' : 'fil' }
         if type_m in tab.keys(): type_m = tab[type_m]
         type_mm = re.sub('-', '', type_m)
@@ -141,6 +144,8 @@ class Ip6tables(object):
                 'wifi-adh-v6' : 'extwifiv6',
                 'serveurs':'extfil' }
         ip = ipv6_addr(mac, type_machine)
+        if not ip:
+            return
         for proto in ['tcp', 'udp']:
             for port in ports[proto]:
                 if port != ':':
@@ -157,6 +162,8 @@ ACCEPT' % (dev, proto, ip, port))
         'wifi-adh-v6' : 'cranswifiv6',
         'serveurs':'cransfil' }
         ip = ipv6_addr(mac, type_machine)
+        if not ip:
+            return
         for proto in ['tcp', 'udp']:
             for port in ports[proto]:
                 if port != ':':
@@ -470,9 +477,7 @@ def check_ip_proto(ip_proto):
 
 def ipv6_addr(mac, net):
     ''' Renvoie l'adresse ipv6 d'auto-configuration de la mac sur le réseau '''
-    mac_s = mac.split(':')
-    eui = hex(int(mac_s[0],16) ^ 0x02)[2:] + ':'.join(mac_s[1:3]) + 'ff:fe' + ':'.join(mac_s[3:5]) + mac_s[5]
-    return re.sub(':/64', eui , prefix[dprefix[net]][0])
+    return ip6tools.mac_to_ipv6(prefix[dprefix[net]][0], mac)
 
 def mac_addr(ipv6):
     ''' Renvoie l'adresse mac de l'ipv6 d'auto-configuration '''