diff --git a/java/org/servalproject/servaldna/AbstractExternalInterface.java b/java/org/servalproject/servaldna/AbstractExternalInterface.java
index 837f3201..fc8a3d94 100644
--- a/java/org/servalproject/servaldna/AbstractExternalInterface.java
+++ b/java/org/servalproject/servaldna/AbstractExternalInterface.java
@@ -12,6 +12,7 @@ import java.nio.channels.SelectionKey;
 public abstract class AbstractExternalInterface  extends ChannelSelector.Handler {
 	private final ChannelSelector selector;
 	protected final MdpSocket socket;
+	private boolean isUp = false;
 
 	public AbstractExternalInterface(ChannelSelector selector, int loopbackMdpPort) throws IOException {
 		this.socket = new MdpSocket(loopbackMdpPort);
@@ -41,9 +42,11 @@ public abstract class AbstractExternalInterface  extends ChannelSelector.Handler
 		packet.payload.put(config.getBytes());
 		packet.payload.flip();
 		packet.send((DatagramChannel)socket.getChannel());
+		isUp = true;
 	}
 
 	public void down() throws IOException {
+		isUp = false;
 		MdpPacket packet = new MdpPacket();
 		packet.setRemotePort(MDP_INTERFACE);
 		packet.payload.put((byte) MDP_INTERFACE_DOWN);
@@ -55,6 +58,9 @@ public abstract class AbstractExternalInterface  extends ChannelSelector.Handler
 		receivedPacket(recvaddr, recvbytes, 0, recvbytes==null?0:recvbytes.length);
 	}
 	public void receivedPacket(byte recvaddr[], byte recvbytes[], int offset, int len) throws IOException {
+		if (!isUp)
+			return;
+
 		MdpPacket packet = new MdpPacket();
 		packet.setRemotePort(MDP_INTERFACE);
 		packet.payload.put((byte) MDP_INTERFACE_RECV);
@@ -73,6 +79,8 @@ public abstract class AbstractExternalInterface  extends ChannelSelector.Handler
 		try {
 			MdpPacket response = new MdpPacket();
 			socket.receive(response);
+			if (!isUp)
+				return;
 			int addrlen = response.payload.get() & 0xFF;
 			byte addr[]=null;
 			if (addrlen>0) {
diff --git a/java/org/servalproject/servaldna/MdpPacket.java b/java/org/servalproject/servaldna/MdpPacket.java
index 6b04d223..d24da9c6 100644
--- a/java/org/servalproject/servaldna/MdpPacket.java
+++ b/java/org/servalproject/servaldna/MdpPacket.java
@@ -12,7 +12,7 @@ public class MdpPacket {
 	private ByteBuffer buff;
 	public ByteBuffer payload;
 
-	private static final int MDP_MTU = 1200;
+	private static final int MDP_MTU = 1400;
 	private static final int HEADER_LEN = 32+4+32+4+1+1+1;
 
 	public static final byte MDP_FLAG_NO_CRYPT = (1<<0);
@@ -26,7 +26,7 @@ public class MdpPacket {
 	public static final int MDP_PORT_SERVICE_DISCOVERY = 11;
 
 	public MdpPacket(){
-		buff = ByteBuffer.allocate(MDP_MTU);
+		buff = ByteBuffer.allocate(MDP_MTU + HEADER_LEN);
 		buff.order(ByteOrder.nativeOrder());
 		buff.position(HEADER_LEN);
 		payload = buff.slice();
diff --git a/overlay_mdp.c b/overlay_mdp.c
index fa4ef0a2..2cf6e7cd 100644
--- a/overlay_mdp.c
+++ b/overlay_mdp.c
@@ -1667,7 +1667,7 @@ static int mdp_send2(struct __sourceloc __whence, const struct socket_address *c
 static void mdp_poll2(struct sched_ent *alarm)
 {
   if (alarm->poll.revents & POLLIN) {
-    uint8_t payload[1200];
+    uint8_t payload[1400];
     struct mdp_header header;
     struct socket_address client;
     bzero(&client, sizeof client);