diff --git a/docs/rh-log.txt b/docs/rh-log.txt
index da3473894..7e9621ba6 100644
--- a/docs/rh-log.txt
+++ b/docs/rh-log.txt
@@ -3,6 +3,11 @@ January 24, 2009  (Changes by Graf Zahl)
 - Fixed: With COMPAT_TRACE switched on linedef actions on lines having
   the same sector on both sides were not triggered.
 
+January 23, 2009
+- Set packet server as the default for four or more player games, and also the
+  default for three player games where the other players are not in the same
+  private IP range.
+
 January 18, 2009  (Changes by Graf Zahl)
 - Added a CopyInfo function to FTexture that contains all code required to 
   clone a texture. Used for creating warping textures.
diff --git a/src/d_net.cpp b/src/d_net.cpp
index 89c4043c0..d480ab61f 100644
--- a/src/d_net.cpp
+++ b/src/d_net.cpp
@@ -1583,12 +1583,16 @@ void D_CheckNetGame (void)
 	}
 
 	// I_InitNetwork sets doomcom and netgame
-	I_InitNetwork ();
+	if (I_InitNetwork ())
+	{
+		NetMode = NET_PacketServer;
+	}
 	if (doomcom.id != DOOMCOM_ID)
+	{
 		I_FatalError ("Doomcom buffer invalid!");
-
+	}
 	players[0].settings_controller = true;
-	
+
 	consoleplayer = doomcom.consoleplayer;
 
 	v = Args->CheckValue ("-netmode");
@@ -1596,6 +1600,11 @@ void D_CheckNetGame (void)
 	{
 		NetMode = atoi (v) != 0 ? NET_PacketServer : NET_PeerToPeer;
 	}
+	if (doomcom.numnodes > 1)
+	{
+		Printf ("Selected " TEXTCOLOR_BLUE "%s" TEXTCOLOR_NORMAL " networking mode. (%s)\n", NetMode == NET_PeerToPeer ? "peer to peer" : "packet server",
+			v != NULL ? "forced" : "auto");
+	}
 
 	// [RH] Setup user info
 	D_SetupUserInfo ();
diff --git a/src/i_net.cpp b/src/i_net.cpp
index e9945d2a5..caa3a61fb 100644
--- a/src/i_net.cpp
+++ b/src/i_net.cpp
@@ -777,10 +777,64 @@ void JoinGame (int i)
 	doomcom.numplayers = doomcom.numnodes;
 }
 
+static int PrivateNetOf(in_addr in)
+{
+	int addr = ntohl(in.s_addr);
+		 if ((addr & 0xFFFF0000) == 0xC0A80000)		// 192.168.0.0
+	{
+		return 0xC0A80000;
+	}
+	else if ((addr & 0xFFF00000) == 0xAC100000)		// 172.16.0.0
+	{
+		return 0xAC100000;
+	}
+	else if ((addr & 0xFF000000) == 0x0A000000)		// 10.0.0.0
+	{
+		return 0x0A000000;
+	}
+	else if ((addr & 0xFF000000) == 0x7F000000)		// 127.0.0.0 (localhost)
+	{
+		return 0x7F000000;
+	}
+	// Not a private IP
+	return 0;
+}
+
+//
+// NodesOnSameNetwork
+//
+// The best I can really do here is check if the others are on the same
+// private network, since that means we (probably) are too.
+//
+
+static bool NodesOnSameNetwork()
+{
+	int net1;
+
+	net1 = PrivateNetOf(sendaddress[1].sin_addr);
+//	Printf("net1 = %08x\n", net1);
+	if (net1 == 0)
+	{
+		return false;
+	}
+	for (int i = 2; i < doomcom.numnodes; ++i)
+	{
+		int net = PrivateNetOf(sendaddress[i].sin_addr);
+//		Printf("Net[%d] = %08x\n", i, net);
+		if (net != net1)
+		{
+			return false;
+		}
+	}
+	return true;
+}
+
 //
 // I_InitNetwork
 //
-void I_InitNetwork (void)
+// Returns true if packet server mode might be a good idea.
+//
+bool I_InitNetwork (void)
 {
 	int i;
 	char *v;
@@ -829,8 +883,14 @@ void I_InitNetwork (void)
 		doomcom.id = DOOMCOM_ID;
 		doomcom.numplayers = doomcom.numnodes = 1;
 		doomcom.consoleplayer = 0;
-		return;
+		return false;
 	}
+	if (doomcom.numnodes < 3)
+	{ // Packet server mode with only two players is effectively the same as
+	  // peer-to-peer but with some slightly larger packets.
+		return false;
+	}
+	return doomcom.numnodes > 3 || !NodesOnSameNetwork();
 }
 
 
diff --git a/src/i_net.h b/src/i_net.h
index b5630c4c1..53e835702 100644
--- a/src/i_net.h
+++ b/src/i_net.h
@@ -24,7 +24,7 @@
 #define __I_NET_H__
 
 // Called by D_DoomMain.
-void I_InitNetwork (void);
+bool I_InitNetwork (void);
 void I_NetCmd (void);
 
 #endif