Index: wp-includes/canonical.php
===================================================================
--- wp-includes/canonical.php	(revision 20399)
+++ wp-includes/canonical.php	(working copy)
@@ -528,6 +528,15 @@
 		wp_redirect( site_url( 'wp-login.php', 'login' ) );
 		exit;
 	}
+
+	$network = array(
+		home_url( 'network', 'relative' ),
+		site_url( 'network', 'relative' ),
+	);
+	if ( in_array( untrailingslashit( $_SERVER['REQUEST_URI'] ), $network ) ) {
+		wp_redirect( network_admin_url() );
+		exit;
+	}
 }
 
 add_action( 'template_redirect', 'wp_redirect_admin_locations', 1000 );