diff --git a/gestion/hptools.py b/gestion/hptools.py
index a6eb6423..f769bc20 100644
--- a/gestion/hptools.py
+++ b/gestion/hptools.py
@@ -127,6 +127,7 @@ class snmp :
         if version == '1' or version == '2c' :
             self.options = "-v %s -c '%s' %s " % ( version, community, host )
         elif version =='3' :
+            self.fetch_engineid()
             self.options = "-v 3 -e %s -u %s -a %s -A '%s' -l authNoPriv" % ( self._engineid, username, authentication_protocol, authentication_pass )
             if privacy_pass :
                 self.options += " -x DES -X '%s' -l authPriv" % privacy_pass
@@ -134,6 +135,13 @@ class snmp :
         else :
             raise ValueError('Version incorrecte')
 
+    def get_mac(self):
+        s, r = getstatusoutput("arp -a %s | perl -nle '{print $& if /00(:[0-9a-f]{2}){5}/}'" % self.host)
+        return r
+
+    def fetch_engineid(self):
+        self._engineid = '0000000b000%s0' % self.get_mac().replace(':', '')
+
     def __init_ldap(self):
         try:
             self._machine = cl.search("host=%(host)s" % {'host': self.host})["machineCrans"][0]
@@ -313,7 +321,7 @@ class hpswitch :
     def nb_prises(self) :
         """ Retourne le nombre de prises du switch """
         if self.__debug : self.__logDest.write("HP DEBUG : nb_prises()\n")
-        return int(findall(r'Switch 26([0-9]{2})', self.version())[0])
+        return int(self.get('SNMPv2-SMI::mib-2.17.1.2.0'))
 
     def version(self) :
         """ Retourne la version du firmware du switch """