diff --git a/libraries/AP_HAL_ChibiOS/hwdef/CubeRedPrimary/hwdef.dat b/libraries/AP_HAL_ChibiOS/hwdef/CubeRedPrimary/hwdef.dat
index a7a89aaae758a..28282794e8720 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/CubeRedPrimary/hwdef.dat
+++ b/libraries/AP_HAL_ChibiOS/hwdef/CubeRedPrimary/hwdef.dat
@@ -176,6 +176,11 @@ PA1  ETH_RMII_REF_CLK   ETH1
 define BOARD_PHY_ID  MII_LAN8720_ID
 define BOARD_PHY_RMII
 
+# PHY link type. Dynamic is the default, but options to force a link speed of 10 or 100 are available.
+define STM32_MAC_PHY_LINK_TYPE MAC_LINK_DYNAMIC
+#define STM32_MAC_PHY_LINK_TYPE MAC_LINK_100_FULLDUPLEX
+#define STM32_MAC_PHY_LINK_TYPE MACLINK_10_FULLDUPLEX
+
 # Refer to https://maclookup.app/vendors/cubepilot-pty-ltd
 # Note, lower 3 bytes (ADDR3,4,5) will be replaced with the platform UUID
 define AP_NETWORKING_DEFAULT_MAC_ADDR "A8:B0:28:00:00:00"