diff --git a/target/linux/ramips/dts/mt7621_haier-sim_wr1800k.dtsi b/target/linux/ramips/dts/mt7621_haier-sim_wr1800k.dtsi
index dd7b72707e..8bd63967c0 100644
--- a/target/linux/ramips/dts/mt7621_haier-sim_wr1800k.dtsi
+++ b/target/linux/ramips/dts/mt7621_haier-sim_wr1800k.dtsi
@@ -67,16 +67,10 @@
 &gmac1 {
 	status = "okay";
 	label = "wan";
-	phy-handle = <&ethphy4>;
-
 	nvmem-cells = <&macaddr_factory_8004 (-3)>;
 	nvmem-cell-names = "mac-address";
 };
 
-&ethphy4 {
-	/delete-property/ interrupts;
-};
-
 &nand {
 	status = "okay";
 
@@ -166,7 +160,6 @@
 	ports {
 		port@1 {
 			status = "okay";
-			label = "lan3";
 		};
 
 		port@2 {
@@ -176,7 +169,6 @@
 
 		port@3 {
 			status = "okay";
-			label = "lan1";
 		};
 	};
 };
diff --git a/target/linux/ramips/dts/mt7621_haier_har-20s2u1.dts b/target/linux/ramips/dts/mt7621_haier_har-20s2u1.dts
index dede7dbb20..8c1b23f8eb 100644
--- a/target/linux/ramips/dts/mt7621_haier_har-20s2u1.dts
+++ b/target/linux/ramips/dts/mt7621_haier_har-20s2u1.dts
@@ -6,3 +6,23 @@
 	compatible = "haier,har-20s2u1", "mediatek,mt7621-soc";
 	model = "Haier HAR-20S2U1";
 };
+
+&ethphy4 {
+	/delete-property/ interrupts;
+};
+
+&gmac1 {
+	phy-handle = <&ethphy4>;
+};
+
+&switch0 {
+	ports {
+		port@1 {
+			label = "lan3";
+		};
+
+		port@3 {
+			label = "lan1";
+		};
+	};
+};
diff --git a/target/linux/ramips/dts/mt7621_sim_simax1800t.dts b/target/linux/ramips/dts/mt7621_sim_simax1800t.dts
index 3c5c9179d2..b75af605bb 100644
--- a/target/linux/ramips/dts/mt7621_sim_simax1800t.dts
+++ b/target/linux/ramips/dts/mt7621_sim_simax1800t.dts
@@ -6,3 +6,23 @@
 	compatible = "sim,simax1800t", "mediatek,mt7621-soc";
 	model = "SIM SIMAX1800T";
 };
+
+&ethphy4 {
+	/delete-property/ interrupts;
+};
+
+&gmac1 {
+	phy-handle = <&ethphy4>;
+};
+
+&switch0 {
+	ports {
+		port@1 {
+			label = "lan3";
+		};
+
+		port@3 {
+			label = "lan1";
+		};
+	};
+};
diff --git a/target/linux/ramips/dts/mt7621_sim_simax1800u.dts b/target/linux/ramips/dts/mt7621_sim_simax1800u.dts
new file mode 100644
index 0000000000..70fff673f5
--- /dev/null
+++ b/target/linux/ramips/dts/mt7621_sim_simax1800u.dts
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0-or-later OR MIT
+
+#include "mt7621_haier-sim_wr1800k.dtsi"
+
+/ {
+	compatible = "sim,simax1800u", "mediatek,mt7621-soc";
+	model = "SIM SIMAX1800U";
+};
+
+&ethphy0 {
+	/delete-property/ interrupts;
+};
+
+&gmac1 {
+	phy-handle = <&ethphy0>;
+};
+
+&switch0 {
+	ports {
+		port@1 {
+			label = "lan1";
+		};
+
+		port@3 {
+			label = "lan3";
+		};
+	};
+};
diff --git a/target/linux/ramips/image/mt7621.mk b/target/linux/ramips/image/mt7621.mk
index 2549f353e9..578c293224 100644
--- a/target/linux/ramips/image/mt7621.mk
+++ b/target/linux/ramips/image/mt7621.mk
@@ -2615,6 +2615,13 @@ define Device/sim_simax1800t
 endef
 TARGET_DEVICES += sim_simax1800t
 
+define Device/sim_simax1800u
+  $(Device/haier-sim_wr1800k)
+  DEVICE_VENDOR := SIM
+  DEVICE_MODEL := SIMAX1800U
+endef
+TARGET_DEVICES += sim_simax1800u
+
 define Device/snr_snr-cpe-me1
   $(Device/dsa-migration)
   $(Device/uimage-lzma-loader)
diff --git a/target/linux/ramips/mt7621/base-files/etc/board.d/02_network b/target/linux/ramips/mt7621/base-files/etc/board.d/02_network
index 1e194fef5f..c12c46dc10 100644
--- a/target/linux/ramips/mt7621/base-files/etc/board.d/02_network
+++ b/target/linux/ramips/mt7621/base-files/etc/board.d/02_network
@@ -22,6 +22,7 @@ ramips_setup_interfaces()
 	mercusys,mr70x-v1|\
 	netgear,wax202|\
 	sim,simax1800t|\
+	sim,simax1800u|\
 	tplink,mr600-v2-eu|\
 	xiaomi,mi-router-3-pro|\
 	xiaomi,mi-router-ac2100|\
diff --git a/target/linux/ramips/mt7621/base-files/etc/hotplug.d/ieee80211/10_fix_wifi_mac b/target/linux/ramips/mt7621/base-files/etc/hotplug.d/ieee80211/10_fix_wifi_mac
index 0c9c98399a..21ab3f16ea 100644
--- a/target/linux/ramips/mt7621/base-files/etc/hotplug.d/ieee80211/10_fix_wifi_mac
+++ b/target/linux/ramips/mt7621/base-files/etc/hotplug.d/ieee80211/10_fix_wifi_mac
@@ -105,7 +105,8 @@ case "$board" in
 		;;
 	haier,har-20s2u1|\
 	jcg,y2|\
-	sim,simax1800t)
+	sim,simax1800t|\
+	sim,simax1800u)
 		[ "$PHYNBR" = "1" ] && \
 			macaddr_setbit_la "$(mtd_get_mac_binary factory 0x4)" > /sys${DEVPATH}/macaddress
 		;;
diff --git a/target/linux/ramips/mt7621/base-files/lib/upgrade/platform.sh b/target/linux/ramips/mt7621/base-files/lib/upgrade/platform.sh
index 9180118f3d..a1f14f9d78 100755
--- a/target/linux/ramips/mt7621/base-files/lib/upgrade/platform.sh
+++ b/target/linux/ramips/mt7621/base-files/lib/upgrade/platform.sh
@@ -138,6 +138,7 @@ platform_do_upgrade() {
 	sercomm,na502|\
 	sercomm,na502s|\
 	sim,simax1800t|\
+	sim,simax1800u|\
 	tplink,ec330-g5u-v1|\
 	wifire,s1500-nbn|\
 	xiaomi,mi-router-3g|\