guests/debian: fix dhcp assigned default to work

CHANGELOG.md

@@ -10,6 +10,8 @@ IMPROVEMENTS:
 BUG FIXES:
 
   - core: box removal of a V1 box works
+  - guests/debian: fix `use_dhcp_assigned_default_route` to work properly.
+    [GH-2648]
   - guests/debian,ubuntu: fix change\_host\_name for FQDNs with trailing
     dots [GH-2610]
   - guests/freebsd: configuring networks in the guest works properly

templates/guests/debian/network_dhcp.erb

@@ -5,7 +5,9 @@ iface eth<%= options[:interface] %> inet dhcp
 <% if !options[:use_dhcp_assigned_default_route] %>
     post-up route del default dev $IFACE
 <% else %>
-    # needed as some newer distribution do not properly load routes, ubuntu 12.04
+    # We need to disable eth0, see GH-2648
+    post-up route del default dev eth0
     post-up dhclient $IFACE
+    pre-down route add default dev eth0
 <% end %>
 #VAGRANT-END