diff -ur a/plugins/huawei/77-mm-huawei-net-port-types.rules b/plugins/huawei/77-mm-huawei-net-port-types.rules
--- a/plugins/huawei/77-mm-huawei-net-port-types.rules
+++ b/plugins/huawei/77-mm-huawei-net-port-types.rules
@@ -8,9 +8,13 @@
 SUBSYSTEMS=="usb", ATTRS{bInterfaceClass}=="ff", ATTRS{bInterfaceSubClass}=="01", ATTRS{bInterfaceProtocol}=="02", ENV{ID_MM_HUAWEI_AT_PORT}="1"
 SUBSYSTEMS=="usb", ATTRS{bInterfaceClass}=="ff", ATTRS{bInterfaceSubClass}=="02", ATTRS{bInterfaceProtocol}=="01", ENV{ID_MM_HUAWEI_MODEM_PORT}="1"
 SUBSYSTEMS=="usb", ATTRS{bInterfaceClass}=="ff", ATTRS{bInterfaceSubClass}=="02", ATTRS{bInterfaceProtocol}=="02", ENV{ID_MM_HUAWEI_AT_PORT}="1"
+# Huawei E3276 firmware 21.192.13.00.00
+SUBSYSTEMS=="usb", ATTRS{bInterfaceClass}=="ff", ATTRS{bInterfaceSubClass}=="02", ATTRS{bInterfaceProtocol}=="12", ENV{ID_MM_HUAWEI_AT_PORT}="1"
 
 # Only the standard ECM or NCM port can support dial-up with AT NDISDUP through AT port
 SUBSYSTEMS=="usb", ATTRS{bInterfaceClass}=="02", ATTRS{bInterfaceSubClass}=="06",ATTRS{bInterfaceProtocol}=="00", ENV{ID_MM_HUAWEI_NDISDUP_SUPPORTED}="1"
 SUBSYSTEMS=="usb", ATTRS{bInterfaceClass}=="02", ATTRS{bInterfaceSubClass}=="0d",ATTRS{bInterfaceProtocol}=="00", ENV{ID_MM_HUAWEI_NDISDUP_SUPPORTED}="1"
+# Huawei E3276 firmware 21.192.13.00.00
+SUBSYSTEMS=="usb", ATTRS{bInterfaceClass}=="ff", ATTRS{bInterfaceSubClass}=="02",ATTRS{bInterfaceProtocol}=="16", ENV{ID_MM_HUAWEI_NDISDUP_SUPPORTED}="1"
 
 LABEL="mm_huawei_port_types_end"
diff -ur a/plugins/huawei/mm-broadband-bearer-huawei.c b/plugins/huawei/mm-broadband-bearer-huawei.c
--- a/plugins/huawei/mm-broadband-bearer-huawei.c
+++ b/plugins/huawei/mm-broadband-bearer-huawei.c
@@ -227,7 +227,10 @@
     case CONNECT_3GPP_CONTEXT_STEP_FIRST: {
         MMBearerIpFamily ip_type;
 
-        ip_type = mm_bearer_properties_get_ip_type (mm_bearer_peek_config (MM_BEARER (ctx->self)));
+        /* Default to IPv4 if not specified */
+        if ((ip_type = mm_bearer_properties_get_ip_type (mm_bearer_peek_config (MM_BEARER (ctx->self)))) == MM_BEARER_IP_FAMILY_UNKNOWN) {
+                ip_type = MM_BEARER_IP_FAMILY_IPV4;
+        }
         if (ip_type != MM_BEARER_IP_FAMILY_IPV4) {
             g_simple_async_result_set_error (ctx->result,
                                              MM_CORE_ERROR,
@@ -256,13 +259,26 @@
         user = mm_bearer_properties_get_user (mm_bearer_peek_config (MM_BEARER (ctx->self)));
         passwd = mm_bearer_properties_get_password (mm_bearer_peek_config (MM_BEARER (ctx->self)));
         auth = mm_bearer_properties_get_allowed_auth (mm_bearer_peek_config (MM_BEARER (ctx->self)));
-        encoded_auth = huawei_parse_auth_type (auth);
+        
+        /* Default to no authentication if not specified */
+        if ((encoded_auth = huawei_parse_auth_type (auth)) == MM_BEARER_HUAWEI_AUTH_UNKNOWN) {
+            encoded_auth = MM_BEARER_HUAWEI_AUTH_NONE;
+        }
 
-        command = g_strdup_printf ("AT^NDISDUP=1,1,\"%s\",\"%s\",\"%s\",%d",
-                                   apn == NULL ? "" : apn,
-                                   user == NULL ? "" : user,
-                                   passwd == NULL ? "" : passwd,
-                                   encoded_auth == MM_BEARER_HUAWEI_AUTH_UNKNOWN ? MM_BEARER_HUAWEI_AUTH_NONE : encoded_auth);
+        if (!user && !passwd) {
+            command = g_strdup ("AT^NDISDUP=1,1");
+        } else if (encoded_auth == MM_BEARER_HUAWEI_AUTH_NONE) {
+		    command = g_strdup_printf ("AT^NDISDUP=1,1,\"%s\",\"%s\",\"%s\"",
+                                       apn == NULL ? "" : apn,
+                                       user == NULL ? "" : user,
+                                       passwd == NULL ? "" : passwd);
+        } else {			
+            command = g_strdup_printf ("AT^NDISDUP=1,1,\"%s\",\"%s\",\"%s\",%d",
+                                       apn == NULL ? "" : apn,
+                                       user == NULL ? "" : user,
+                                       passwd == NULL ? "" : passwd,
+                                       encoded_auth);
+        }
         mm_base_modem_at_command_full (ctx->modem,
                                        ctx->primary,
                                        command,