+ # parent device and ifname
+ local p_device p_type
+ config_get p_device "$cfg" device
+ config_get p_type "$cfg" type
+
+ # select alias ifname
+ local layer use_iface
+ config_get layer "$config" layer 2
+ case "$layer:$p_type" in
+ # layer 3: e.g. pppoe-wan or pptp-vpn
+ 3:*) use_iface="$iface" ;;
+
+ # layer 2 and parent is bridge: e.g. br-wan
+ 2:bridge) use_iface="br-$cfg" ;;
+
+ # layer 1: e.g. eth0 or ath0
+ *) use_iface="$p_device" ;;
+ esac
+