diff --git a/src/include/ipxe/netdevice.h b/src/include/ipxe/netdevice.h
index 6ef9cb1e..95ad1cf1 100644
--- a/src/include/ipxe/netdevice.h
+++ b/src/include/ipxe/netdevice.h
@@ -685,6 +685,8 @@ extern struct net_device * find_netdev ( const char *name );
 extern struct net_device * find_netdev_by_index ( unsigned int index );
 extern struct net_device * find_netdev_by_location ( unsigned int bus_type,
 						     unsigned int location );
+extern struct net_device *
+find_netdev_by_ll_addr ( struct ll_protocol *ll_protocol, const void *ll_addr );
 extern struct net_device * last_opened_netdev ( void );
 extern int net_tx ( struct io_buffer *iobuf, struct net_device *netdev,
 		    struct net_protocol *net_protocol, const void *ll_dest,
diff --git a/src/net/netdevice.c b/src/net/netdevice.c
index 2350256f..a8020858 100644
--- a/src/net/netdevice.c
+++ b/src/net/netdevice.c
@@ -602,9 +602,27 @@ struct net_device * alloc_netdev ( size_t priv_len ) {
 int register_netdev ( struct net_device *netdev ) {
 	struct ll_protocol *ll_protocol = netdev->ll_protocol;
 	struct net_driver *driver;
+	struct net_device *duplicate;
 	uint32_t seed;
 	int rc;
 
+	/* Set initial link-layer address, if not already set */
+	if ( ! netdev_has_ll_addr ( netdev ) ) {
+		ll_protocol->init_addr ( netdev->hw_addr, netdev->ll_addr );
+	}
+
+	/* Reject network devices that are already available via a
+	 * different hardware device.
+	 */
+	duplicate = find_netdev_by_ll_addr ( ll_protocol, netdev->ll_addr );
+	if ( duplicate && ( duplicate->dev != netdev->dev ) ) {
+		DBGC ( netdev, "NETDEV rejecting duplicate (phys %s) of %s "
+		       "(phys %s)\n", netdev->dev->name, duplicate->name,
+		       duplicate->dev->name );
+		rc = -EEXIST;
+		goto err_duplicate;
+	}
+
 	/* Record device index and create device name */
 	netdev->index = netdev_index++;
 	if ( netdev->name[0] == '\0' ) {
@@ -612,11 +630,6 @@ int register_netdev ( struct net_device *netdev ) {
 			   netdev->index );
 	}
 
-	/* Set initial link-layer address, if not already set */
-	if ( ! netdev_has_ll_addr ( netdev ) ) {
-		ll_protocol->init_addr ( netdev->hw_addr, netdev->ll_addr );
-	}
-
 	/* Use least significant bits of the link-layer address to
 	 * improve the randomness of the (non-cryptographic) random
 	 * number generator.
@@ -660,6 +673,7 @@ int register_netdev ( struct net_device *netdev ) {
 	clear_settings ( netdev_settings ( netdev ) );
 	unregister_settings ( netdev_settings ( netdev ) );
  err_register_settings:
+ err_duplicate:
 	return rc;
 }
 
@@ -852,6 +866,27 @@ struct net_device * find_netdev_by_location ( unsigned int bus_type,
 	return NULL;	
 }
 
+/**
+ * Get network device by link-layer address
+ *
+ * @v ll_protocol	Link-layer protocol
+ * @v ll_addr		Link-layer address
+ * @ret netdev		Network device, or NULL
+ */
+struct net_device * find_netdev_by_ll_addr ( struct ll_protocol *ll_protocol,
+					     const void *ll_addr ) {
+	struct net_device *netdev;
+
+	list_for_each_entry ( netdev, &net_devices, list ) {
+		if ( ( netdev->ll_protocol == ll_protocol ) &&
+		     ( memcmp ( netdev->ll_addr, ll_addr,
+				ll_protocol->ll_addr_len ) == 0 ) )
+			return netdev;
+	}
+
+	return NULL;
+}
+
 /**
  * Get most recently opened network device
  *