diff --git a/arch/arm/boot/dts/bcm47094-asus-rt-ac88u.dts b/arch/arm/boot/dts/bcm47094-asus-rt-ac88u.dts
index cf793c558437..5696dd5fbaf4 100644
--- a/arch/arm/boot/dts/bcm47094-asus-rt-ac88u.dts
+++ b/arch/arm/boot/dts/bcm47094-asus-rt-ac88u.dts
@@ -205,6 +205,7 @@ port@4 {
 		sw0_p5: port@5 {
 			reg = <5>;
 			label = "extsw";
+			phy-mode = "rgmii";
 
 			fixed-link {
 				speed = <1000>;