You can configure backup relations between a pair of any Layer 2 interfaces, except the VLAN interface. A backup interface is activated when the primary interface fails. The backup interface is deactivated when the primary interface is restored. A Dialer interface, FastEthernet interface, GRE tunnel interface, or Loopback interface can serve as a backup interface to a FastEthernet interface, GRE tunnel interface, or Loopback interface on the same module.