Check for adapter collisions

lib/vagrant/action/vm/network.rb

@@ -46,6 +46,9 @@ module Vagrant
           @logger.debug("Assigning adapter locations...")
           assign_adapter_locations(adapters)
 
+          # Verify that our adapters are good just prior to enabling them.
+          verify_adapters(adapters)
+
           # Create all the network interfaces
           @logger.info("Enabling adapters...")
           env[:ui].info I18n.t("vagrant.actions.vm.network.preparing")
@@ -100,6 +103,17 @@ module Vagrant
           end
         end
 
+        # Verifies that the adapter configurations look good. This will
+        # raise an exception in the case that any errors occur.
+        def verify_adapters(adapters)
+          # Verify that there are no collisions in the adapters being used.
+          used = Set.new
+          adapters.each do |adapter|
+            raise Errors::NetworkAdapterCollision if used.include?(adapter[:adapter])
+            used.add(adapter[:adapter])
+          end
+        end
+
         # Assigns the actual interface number of a network based on the
         # enabled NICs on the virtual machine.
         #

lib/vagrant/errors.rb

@@ -203,6 +203,11 @@ module Vagrant
       error_key(:multi_vm_target_required)
     end
 
+    class NetworkAdapterCollision < VagrantError
+      status_code(65)
+      error_key(:adapter_collision, "vagrant.actions.vm.network")
+    end
+
     class NetworkCollision < VagrantError
       status_code(29)
       error_key(:collides, "vagrant.actions.vm.host_only_network")

templates/locales/en.yml

@@ -395,6 +395,10 @@ en:
             MAC address is typically up to the box and box maintiner. Please contact
             the relevant person to solve this issue.
         network:
+          adapter_collision: |-
+            More than one network have been assigned to the same adapter. At
+            this point this error is actually indicative of an internal error
+            within Vagrant. Please report this as a bug.
           configuring: |-
             Configuring and enabling network interfaces...
           no_adapters: |-