diff --git a/nat/pmp.go b/nat/pmp.go
index f35ce5c0..f3c726f5 100644
--- a/nat/pmp.go
+++ b/nat/pmp.go
@@ -65,10 +65,6 @@ func (p *PMP) AddPortMapping(port uint16) error {
 	p.forwardedPortsMtx.Lock()
 	defer p.forwardedPortsMtx.Unlock()
 
-	if _, exists := p.forwardedPorts[port]; exists {
-		return nil
-	}
-
 	_, err := p.client.AddPortMapping("tcp", int(port), int(port), 0)
 	if err != nil {
 		return err
diff --git a/nat/upnp.go b/nat/upnp.go
index 4022456a..c533640b 100644
--- a/nat/upnp.go
+++ b/nat/upnp.go
@@ -62,10 +62,6 @@ func (u *UPnP) AddPortMapping(port uint16) error {
 	u.forwardedPortsMtx.Lock()
 	defer u.forwardedPortsMtx.Unlock()
 
-	if _, exists := u.forwardedPorts[port]; exists {
-		return nil
-	}
-
 	if err := u.device.Forward(port, ""); err != nil {
 		return err
 	}
diff --git a/server.go b/server.go
index 2539745c..8a0275ba 100644
--- a/server.go
+++ b/server.go
@@ -1145,6 +1145,21 @@ out:
 				continue
 			}
 
+			// Periodically renew the NAT port forwarding.
+			for _, port := range forwardedPorts {
+				err := s.natTraversal.AddPortMapping(port)
+				if err != nil {
+					srvrLog.Warnf("Unable to automatically "+
+						"re-create port forwarding using %s: %v",
+						s.natTraversal.Name(), err)
+				} else {
+					srvrLog.Debugf("Automatically re-created "+
+						"forwarding for port %d using %s to "+
+						"advertise external IP",
+						port, s.natTraversal.Name())
+				}
+			}
+
 			if ip.Equal(s.lastDetectedIP) {
 				continue
 			}