@@ -275,12 +275,11 @@ func (n *networkRouter) postNetworkConnect(ctx context.Context, w http.ResponseW

 		return err

 	}

-	// Always make sure there is no ambiguity with respect to the network ID/name

-	nw, err := n.backend.FindNetwork(vars["id"])

-	if err != nil {

-		return err

-	}

-	return n.backend.ConnectContainerToNetwork(connect.Container, nw.ID(), connect.EndpointConfig)

+	// Unlike other operations, we does not check ambiguity of the name/ID here.

+	// The reason is that, In case of attachable network in swarm scope, the actual local network

+	// may not be available at the time. At the same time, inside daemon `ConnectContainerToNetwork`

+	// does the ambiguity check anyway. Therefore, passing the name to daemon would be enough.

+	return n.backend.ConnectContainerToNetwork(connect.Container, vars["id"], connect.EndpointConfig)

 }

 func (n *networkRouter) postNetworkDisconnect(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {

@@ -20,6 +20,7 @@ import (

 	"github.com/docker/docker/runconfig"

 	"github.com/docker/go-connections/nat"

 	"github.com/docker/libnetwork"

+	netconst "github.com/docker/libnetwork/datastore"

 	"github.com/docker/libnetwork/netlabel"

 	"github.com/docker/libnetwork/options"

 	"github.com/docker/libnetwork/types"

@@ -259,6 +260,13 @@ func (daemon *Daemon) updateNetworkSettings(container *container.Container, n li

 		}

 		if sn.Name() == n.Name() {

+			// If the network scope is swarm, then this

+			// is an attachable network, which may not

+			// be locally available previously.

+			// So always update.

+			if n.Info().Scope() == netconst.SwarmScope {

+				continue

+			}

 			// Avoid duplicate config

 			return nil

 		}

@@ -272,10 +280,8 @@ func (daemon *Daemon) updateNetworkSettings(container *container.Container, n li

 		}

 	}

-	if _, ok := container.NetworkSettings.Networks[n.Name()]; !ok {

-		container.NetworkSettings.Networks[n.Name()] = &network.EndpointSettings{

-			EndpointSettings: endpointConfig,

-		}

+	container.NetworkSettings.Networks[n.Name()] = &network.EndpointSettings{

+		EndpointSettings: endpointConfig,

 	}

 	return nil