Change the default multicast group range

The 224.0.0.X range is a special range in multicast which acts like a
broadcast for non-IGMP traffic.

This patch changes the value of the multicast_group_range configuration
option to 225.0.0.X to avoid this special case.

See session "2.1.2.  Data Forwarding Rules" at
https://tools.ietf.org/html/rfc4541 for more information:

   2) Packets with a destination IP (DIP) address in the 224.0.0.X range
         which are not IGMP must be forwarded on all ports.

Change-Id: Ic8fd860fa7ad6b5401297254e56a796c98bb037a
Signed-off-by: Lucas Alvares Gomes <lucasagomes@gmail.com>
diff --git a/neutron_tempest_plugin/config.py b/neutron_tempest_plugin/config.py
index 51fbafc..2f2f913 100644
--- a/neutron_tempest_plugin/config.py
+++ b/neutron_tempest_plugin/config.py
@@ -67,7 +67,7 @@
 
     # Multicast tests settings
     cfg.StrOpt('multicast_group_range',
-               default='224.0.0.120-224.0.0.250',
+               default='225.0.0.120-225.0.0.250',
                help='Unallocated multi-cast IPv4 range, which will be used to '
                     'test the multi-cast support.'),