diff --git a/usb-ctrl/usb-ctrl b/usb-ctrl/usb-ctrl
index 943e7d4..f9711ef 100644
--- a/usb-ctrl/usb-ctrl
+++ b/usb-ctrl/usb-ctrl
@@ -202,8 +202,12 @@
             echo "${storage}" > "${gadget_function}/lun.0/file"
             ;;
         ecm|eem|rndis)
-            echo "${bmc_mac}" > "${gadget_function}/dev_addr"
-            echo "${host_mac}" > "${gadget_function}/host_addr"
+            if [[ -n ${bmc_mac} && "${bmc_mac}" != "." ]]; then
+                echo "${bmc_mac}" > "${gadget_function}/dev_addr"
+            fi
+            if [[ -n "${host_mac}" ]]; then
+                echo "${host_mac}" > "${gadget_function}/host_addr"
+            fi
             ;;
     esac
     if [ "${is_multifunction}" = false ]; then