diff --git a/src/emu/dinetwork.cpp b/src/emu/dinetwork.cpp
index 094d3476af1..cc1c4402759 100644
--- a/src/emu/dinetwork.cpp
+++ b/src/emu/dinetwork.cpp
@@ -10,6 +10,7 @@ device_network_interface::device_network_interface(const machine_config &mconfig
 	m_bandwidth = bandwidth;
 	set_mac("\0\0\0\0\0\0");
 	m_intf = 0;
+	m_loopback_control = false;
 }
 
 device_network_interface::~device_network_interface()
@@ -22,14 +23,30 @@ void device_network_interface::interface_pre_start()
 	m_recv_timer = device().machine().scheduler().timer_alloc(timer_expired_delegate(FUNC(device_network_interface::recv_complete), this));
 }
 
-int device_network_interface::send(u8 *buf, int len) const
+void device_network_interface::interface_post_start()
+{
+	device().save_item(NAME(m_loopback_control));
+}
+
+int device_network_interface::send(u8 *buf, int len)
 {
 	// TODO: enable this check when other devices implement delayed transmit
 	//assert_always(!m_send_timer->enabled(), "attempted to transmit while transmit already in progress");
 
 	int result = 0;
 
-	if (m_dev)
+	if (m_loopback_control)
+	{
+		// loop data back to receiver
+		result = recv_start_cb(buf, len);
+
+		if (result)
+		{
+			// schedule receive complete callback
+			m_recv_timer->adjust(attotime::from_ticks(len, m_bandwidth * 1'000'000 / 8), result);
+		}
+	}
+	else if (m_dev)
 	{
 		// send the data
 		result = m_dev->send(buf, len);
@@ -50,8 +67,11 @@ void device_network_interface::recv_cb(u8 *buf, int len)
 {
 	assert_always(!m_recv_timer->enabled(), "attempted to receive while receive already in progress");
 
+	int result = 0;
+
 	// process the received data
-	int result = recv_start_cb(buf, len);
+	if (!m_loopback_control)
+		result = recv_start_cb(buf, len);
 
 	if (result)
 	{
@@ -69,7 +89,7 @@ TIMER_CALLBACK_MEMBER(device_network_interface::recv_complete)
 	recv_complete_cb(param);
 
 	// start receiving data from the network again
-	if (m_dev)
+	if (m_dev && !m_loopback_control)
 		m_dev->start();
 }
 
@@ -96,3 +116,19 @@ void device_network_interface::set_interface(int id)
 	}
 	m_intf = id;
 }
+
+void device_network_interface::set_loopback(bool loopback)
+{
+	if (m_loopback_control == loopback)
+		return;
+
+	m_loopback_control = loopback;
+
+	if (m_dev)
+	{
+		if (loopback)
+			m_dev->stop();
+		else if (!m_recv_timer->enabled())
+			m_dev->start();
+	}
+}
diff --git a/src/emu/dinetwork.h b/src/emu/dinetwork.h
index fa5ee730a87..d844be951ab 100644
--- a/src/emu/dinetwork.h
+++ b/src/emu/dinetwork.h
@@ -12,16 +12,18 @@ public:
 	virtual ~device_network_interface();
 
 	void interface_pre_start() override;
+	void interface_post_start() override;
 
 	void set_interface(int id);
 	void set_promisc(bool promisc);
 	void set_mac(const char *mac);
+	void set_loopback(bool loopback);
 
 	const char *get_mac() const { return m_mac; }
 	bool get_promisc() const { return m_promisc; }
 	int get_interface() const { return m_intf; }
 
-	int send(u8 *buf, int len) const;
+	int send(u8 *buf, int len);
 
 	// TODO: de-virtualise this when existing devices implement delayed receive
 	virtual void recv_cb(u8 *buf, int len);
@@ -40,6 +42,7 @@ protected:
 	float m_bandwidth;
 	std::unique_ptr<osd_netdev> m_dev;
 	int m_intf;
+	bool m_loopback_control;
 
 	emu_timer *m_send_timer;
 	emu_timer *m_recv_timer;
diff --git a/src/mame/drivers/sun2.cpp b/src/mame/drivers/sun2.cpp
index c7efe8fa685..e63f5d6560f 100644
--- a/src/mame/drivers/sun2.cpp
+++ b/src/mame/drivers/sun2.cpp
@@ -509,7 +509,7 @@ uint8_t sun2_state::ethernet_r()
 void sun2_state::ethernet_w(uint8_t data)
 {
 	m_edlc->reset_w(!BIT(data, 7));
-	// Bit 6 = loopback control (active low, though inverted for MB502)
+	m_edlc->set_loopback(!BIT(data, 6)); // LBC on MB502
 	m_edlc->ca(BIT(data, 5));
 
 	m_ethernet_status = (data & 0xf0) | (m_ethernet_status & 0x0f);
@@ -570,6 +570,7 @@ void sun2_state::vmetype1space_map(address_map &map)
 	// 7f1000-7f17ff: AM9518 encryption processor
 	//AM_RANGE(0x7f1800, 0x7f1801) AM_DEVREADWRITE8(SCC1_TAG, z80scc_device, cb_r, cb_w, 0xff00)
 	//AM_RANGE(0x7f1802, 0x7f1803) AM_DEVREADWRITE8(SCC1_TAG, z80scc_device, db_r, db_w, 0xff00)
+	map(0x7f1804, 0x7f1805).nopr();
 	//AM_RANGE(0x7f1804, 0x7f1805) AM_DEVREADWRITE8(SCC1_TAG, z80scc_device, ca_r, ca_w, 0xff00)
 	//AM_RANGE(0x7f1806, 0x7f1807) AM_DEVREADWRITE8(SCC1_TAG, z80scc_device, da_r, da_w, 0xff00)
 	map(0x7f2000, 0x7f2000).rw(SCC2_TAG, FUNC(z80scc_device::cb_r), FUNC(z80scc_device::cb_w));