code: func (ncc *SeesawNCC) LBInterfaceUp(iface *ncctypes.LBInterface, out *int) error {
  	// TODO(jsing): Handle IPv6-only, and improve IPv6 route setup.
  	netIface, err := iface.Interface()
  	if err != nil {
  		return err
  	}
  	nodeIface, err := net.InterfaceByName(iface.NodeInterface)
  	if err != nil {
  		return fmt.Errorf("Failed to get node interface: %v", err)
  	}
  	nodeNet, err := findNetwork(nodeIface, iface.Node.IPv4Addr)
  	if err != nil {
  		return fmt.Errorf("Failed to get node network: %v", err)
  	}
  
  	log.Infof("Bringing up LB interface %s on %s", nodeNet, iface.Name)
  
  	if !nodeNet.Contains(iface.ClusterVIP.IPv4Addr) {
  		return fmt.Errorf("Node network %s does not contain cluster VIP %s", nodeNet, iface.ClusterVIP.IPv4Addr)
  	}
  
  	gateway, err := routeDefaultIPv4()
  	if err != nil {
  		return fmt.Errorf("Failed to get IPv4 default route: %v", err)
  	}
  
  	if err := ifaceUp(netIface); err != nil {
  		return fmt.Errorf("Failed to bring interface up: %v", err)
  	}
  
  	// Configure routing.
  	if err := ipRunIface(netIface, "route add %s dev %s table %d", nodeNet, iface.Name, iface.RoutingTableID); err != nil {
  		return fmt.Errorf("Failed to configure routing: %v", err)
  	}
  	if err := ipRunIface(netIface, "route add 0/0 via %s dev %s table %d", gateway, iface.Name, iface.RoutingTableID); err != nil {
  		return fmt.Errorf("Failed to configure routing: %v", err)
  	}
  
  	return nil
  }
docs: // LBInterfaceUp brings the load balancing interface up.