diff --git a/hostapd/main.c b/hostapd/main.c
index 6c7406af4..72b1d91d0 100644
--- a/hostapd/main.c
+++ b/hostapd/main.c
@@ -456,6 +456,7 @@ static void usage(void)
 		"   -T = record to Linux tracing in addition to logging\n"
 		"        (records all messages regardless of debug verbosity)\n"
 #endif /* CONFIG_DEBUG_LINUX_TRACING */
+		"   -S   start all the interfaces synchronously\n"
 		"   -t   include timestamps in some debug messages\n"
 		"   -v   show hostapd version\n");
 
@@ -570,6 +571,7 @@ int main(int argc, char *argv[])
 #ifdef CONFIG_DEBUG_LINUX_TRACING
 	int enable_trace_dbg = 0;
 #endif /* CONFIG_DEBUG_LINUX_TRACING */
+	int start_ifaces_in_sync = 0;
 
 	if (os_program_init())
 		return -1;
@@ -587,7 +589,7 @@ int main(int argc, char *argv[])
 	interfaces.global_ctrl_dst = NULL;
 
 	for (;;) {
-		c = getopt(argc, argv, "b:Bde:f:hKP:Ttu:vg:G:");
+		c = getopt(argc, argv, "b:Bde:f:hKP:STtu:vg:G:");
 		if (c < 0)
 			break;
 		switch (c) {
@@ -644,6 +646,9 @@ int main(int argc, char *argv[])
 			bss_config = tmp_bss;
 			bss_config[num_bss_configs++] = optarg;
 			break;
+		case 'S':
+			start_ifaces_in_sync = 1;
+			break;
 #ifdef CONFIG_WPS
 		case 'u':
 			return gen_uuid(optarg);
@@ -712,6 +717,8 @@ int main(int argc, char *argv[])
 			wpa_printf(MSG_ERROR, "Failed to initialize interface");
 			goto out;
 		}
+		if (start_ifaces_in_sync)
+			interfaces.iface[i]->need_to_start_in_sync = 1;
 	}
 
 	/* Allocate and parse configuration for per-BSS files */
diff --git a/src/ap/hostapd.c b/src/ap/hostapd.c
index 5b95989cf..b10b454e3 100644
--- a/src/ap/hostapd.c
+++ b/src/ap/hostapd.c
@@ -1510,15 +1510,8 @@ void fst_hostapd_fill_iface_obj(struct hostapd_data *hapd,
 #endif /* CONFIG_FST */
 
 
-/**
- * hostapd_setup_interface_complete - Complete interface setup
- *
- * This function is called when previous steps in the interface setup has been
- * completed. This can also start operations, e.g., DFS, that will require
- * additional processing before interface is ready to be enabled. Such
- * operations will call this function from eloop callbacks when finished.
- */
-int hostapd_setup_interface_complete(struct hostapd_iface *iface, int err)
+static int hostapd_setup_interface_complete_sync(struct hostapd_iface *iface,
+						 int err)
 {
 	struct hostapd_data *hapd = iface->bss[0];
 	size_t j;
@@ -1720,6 +1713,89 @@ fail:
 }
 
 
+/**
+ * hostapd_setup_interface_complete - Complete interface setup
+ *
+ * This function is called when previous steps in the interface setup has been
+ * completed. This can also start operations, e.g., DFS, that will require
+ * additional processing before interface is ready to be enabled. Such
+ * operations will call this function from eloop callbacks when finished.
+ */
+int hostapd_setup_interface_complete(struct hostapd_iface *iface, int err)
+{
+	struct hapd_interfaces *interfaces = iface->interfaces;
+	struct hostapd_data *hapd = iface->bss[0];
+	unsigned int i;
+	int not_ready_in_sync_ifaces = 0;
+
+	if (!iface->need_to_start_in_sync)
+		return hostapd_setup_interface_complete_sync(iface, err);
+
+	if (err) {
+		wpa_printf(MSG_ERROR, "Interface initialization failed");
+		hostapd_set_state(iface, HAPD_IFACE_DISABLED);
+		iface->need_to_start_in_sync = 0;
+		wpa_msg(hapd->msg_ctx, MSG_INFO, AP_EVENT_DISABLED);
+		if (interfaces && interfaces->terminate_on_error)
+			eloop_terminate();
+		return -1;
+	}
+
+	if (iface->ready_to_start_in_sync) {
+		/* Already in ready and waiting. should never happpen */
+		return 0;
+	}
+
+	for (i = 0; i < interfaces->count; i++) {
+		if (interfaces->iface[i]->need_to_start_in_sync &&
+		    !interfaces->iface[i]->ready_to_start_in_sync)
+			not_ready_in_sync_ifaces++;
+	}
+
+	/*
+	 * Check if this is the last interface, if yes then start all the other
+	 * waiting interfaces. If not, add this interface to the waiting list.
+	 */
+	if (not_ready_in_sync_ifaces > 1 && iface->state == HAPD_IFACE_DFS) {
+		/*
+		 * If this interface went through CAC, do not synchronize, just
+		 * start immediately.
+		 */
+		iface->need_to_start_in_sync = 0;
+		wpa_printf(MSG_INFO,
+			   "%s: Finished CAC - bypass sync and start interface",
+			   iface->bss[0]->conf->iface);
+		return hostapd_setup_interface_complete_sync(iface, err);
+	}
+
+	if (not_ready_in_sync_ifaces > 1) {
+		/* need to wait as there are other interfaces still coming up */
+		iface->ready_to_start_in_sync = 1;
+		wpa_printf(MSG_INFO,
+			   "%s: Interface waiting to sync with other interfaces",
+			   iface->bss[0]->conf->iface);
+		return 0;
+	}
+
+	wpa_printf(MSG_INFO,
+		   "%s: Last interface to sync - starting all interfaces",
+		   iface->bss[0]->conf->iface);
+	iface->need_to_start_in_sync = 0;
+	hostapd_setup_interface_complete_sync(iface, err);
+	for (i = 0; i < interfaces->count; i++) {
+		if (interfaces->iface[i]->need_to_start_in_sync &&
+		    interfaces->iface[i]->ready_to_start_in_sync) {
+			hostapd_setup_interface_complete_sync(
+				interfaces->iface[i], 0);
+			/* Only once the interfaces are sync started */
+			interfaces->iface[i]->need_to_start_in_sync = 0;
+		}
+	}
+
+	return 0;
+}
+
+
 /**
  * hostapd_setup_interface - Setup of an interface
  * @iface: Pointer to interface data.
diff --git a/src/ap/hostapd.h b/src/ap/hostapd.h
index 024d25fcb..8161a5933 100644
--- a/src/ap/hostapd.h
+++ b/src/ap/hostapd.h
@@ -329,6 +329,15 @@ struct hostapd_iface {
 	 */
 	unsigned int driver_ap_teardown:1;
 
+	/*
+	 * When set, indicates that this interface is part of list of
+	 * interfaces that need to be started together (synchronously).
+	 */
+	unsigned int need_to_start_in_sync:1;
+
+	/* Ready to start but waiting for other interfaces to become ready. */
+	unsigned int ready_to_start_in_sync:1;
+
 	int num_ap; /* number of entries in ap_list */
 	struct ap_info *ap_list; /* AP info list head */
 	struct ap_info *ap_hash[STA_HASH_SIZE];