diff --git a/board/CZ.NIC/turris_common.c b/board/CZ.NIC/turris_common.c
new file mode 100644
index 0000000..1717dda
--- /dev/null
+++ b/board/CZ.NIC/turris_common.c
@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2017 Marek Behún <kabel@kernel.org>
+ */
+
+#include <env.h>
+#include <net.h>
+
+#include "turris_common.h"
+
+static void increment_mac(u8 *mac)
+{
+	int i;
+
+	for (i = 5; i >= 3; i--) {
+		mac[i] += 1;
+		if (mac[i])
+			break;
+	}
+}
+
+static void set_mac_if_invalid(int i, u8 *mac)
+{
+	u8 oldmac[6];
+
+	if (is_valid_ethaddr(mac) &&
+	    !eth_env_get_enetaddr_by_index("eth", i, oldmac))
+		eth_env_set_enetaddr_by_index("eth", i, mac);
+}
+
+void turris_init_mac_addresses(int first_idx, const u8 *first_mac)
+{
+	u8 mac[6];
+
+	memcpy(mac, first_mac, sizeof(mac));
+
+	set_mac_if_invalid((first_idx + 0) % 3, mac);
+	increment_mac(mac);
+	set_mac_if_invalid((first_idx + 1) % 3, mac);
+	increment_mac(mac);
+	set_mac_if_invalid((first_idx + 2) % 3, mac);
+}