diff --git a/router/connection_maker.go b/router/connection_maker.go
index bcf0f96215..50582d947d 100644
--- a/router/connection_maker.go
+++ b/router/connection_maker.go
@@ -19,7 +19,7 @@ type ConnectionMaker struct {
 	peers             *Peers
 	normalisePeerAddr func(string) string
 	targets           map[string]*Target
-	cmdLinePeers      map[string]string
+	cmdLinePeers      map[string]*CmdLinePeer
 	actionChan        chan<- ConnectionMakerAction
 }
 
@@ -31,6 +31,11 @@ type Target struct {
 	tryInterval time.Duration // backoff time on next failure
 }
 
+type CmdLinePeer struct {
+	address      string // normalised and resolved address of peer to connect to
+	portSupplied bool   // did the original address contain a port?
+}
+
 type ConnectionMakerAction func() bool
 
 func NewConnectionMaker(ourself *LocalPeer, peers *Peers, normalisePeerAddr func(string) string) *ConnectionMaker {
@@ -38,7 +43,7 @@ func NewConnectionMaker(ourself *LocalPeer, peers *Peers, normalisePeerAddr func
 		ourself:           ourself,
 		peers:             peers,
 		normalisePeerAddr: normalisePeerAddr,
-		cmdLinePeers:      make(map[string]string),
+		cmdLinePeers:      make(map[string]*CmdLinePeer),
 		targets:           make(map[string]*Target)}
 }
 
@@ -49,14 +54,15 @@ func (cm *ConnectionMaker) Start() {
 }
 
 func (cm *ConnectionMaker) InitiateConnection(peer string) error {
-	addr, err := net.ResolveTCPAddr("tcp4", cm.normalisePeerAddr(peer))
+	normalisedPeerAddr := cm.normalisePeerAddr(peer)
+	addr, err := net.ResolveTCPAddr("tcp4", normalisedPeerAddr)
 	if err != nil {
 		return err
 	}
 	address := addr.String()
-
+	portSupplied := peer == normalisedPeerAddr
 	cm.actionChan <- func() bool {
-		cm.cmdLinePeers[peer] = address
+		cm.cmdLinePeers[peer] = &CmdLinePeer{address: address, portSupplied: portSupplied}
 		// curtail any existing reconnect interval
 		if target, found := cm.targets[address]; found {
 			target.tryAfter, target.tryInterval = tryImmediately()
@@ -138,7 +144,7 @@ func (cm *ConnectionMaker) checkStateAndAttemptConnections() time.Duration {
 	// Copy the set of things we are connected to, so we can access
 	// them without locking.  Also clear out any entries in cm.targets
 	// for existing connections.
-	ourConnectedPeers, ourConnectedTargets := cm.ourConnections()
+	ourConnectedPeers, ourConnectedTargets, ourInboundIPs := cm.ourConnections()
 
 	addTarget := func(address string) {
 		if _, connected := ourConnectedTargets[address]; connected {
@@ -154,9 +160,18 @@ func (cm *ConnectionMaker) checkStateAndAttemptConnections() time.Duration {
 	}
 
 	// Add command-line targets that are not connected
-	for _, address := range cm.cmdLinePeers {
-		addTarget(address)
-		cmdLineTarget[address] = void
+	for _, cmdLinePeer := range cm.cmdLinePeers {
+		cmdLineTarget[cmdLinePeer.address] = void
+		// if a peer was specified w/o a port, then do not connect to
+		// it if we have inbound connections from that IP.
+		if !cmdLinePeer.portSupplied {
+			if ip, _, err := net.SplitHostPort(cmdLinePeer.address); err == nil { // should always succeed
+				if _, connected := ourInboundIPs[ip]; connected {
+					continue
+				}
+			}
+		}
+		addTarget(cmdLinePeer.address)
 	}
 
 	// Add targets for peers that someone else is connected to, but we
@@ -166,18 +181,25 @@ func (cm *ConnectionMaker) checkStateAndAttemptConnections() time.Duration {
 	return cm.connectToTargets(validTarget, cmdLineTarget)
 }
 
-func (cm *ConnectionMaker) ourConnections() (PeerNameSet, map[string]struct{}) {
+func (cm *ConnectionMaker) ourConnections() (PeerNameSet, map[string]struct{}, map[string]struct{}) {
 	var (
 		ourConnectedPeers   = make(PeerNameSet)
 		ourConnectedTargets = make(map[string]struct{})
+		ourInboundIPs       = make(map[string]struct{})
 	)
 	for conn := range cm.ourself.Connections() {
 		address := conn.RemoteTCPAddr()
+		delete(cm.targets, address)
 		ourConnectedPeers[conn.Remote().Name] = void
 		ourConnectedTargets[address] = void
-		delete(cm.targets, address)
+		if conn.Outbound() {
+			continue
+		}
+		if ip, _, err := net.SplitHostPort(address); err == nil { // should always succeed
+			ourInboundIPs[ip] = void
+		}
 	}
-	return ourConnectedPeers, ourConnectedTargets
+	return ourConnectedPeers, ourConnectedTargets, ourInboundIPs
 }
 
 func (cm *ConnectionMaker) addPeerTargets(ourConnectedPeers PeerNameSet, addTarget func(string)) {