The Interface State Control feature allows NHRP to control the state of the interface based on whether the tunnels on the
interface are live. If NHRP detects that all NHSs configured on the interface are in the down state, NHRP can change the interface
state to down. However, if NHRP detects that any one of the NHSs configured on the interface is up, then it can change the
state of the interface to up.
When the NHRP changes the interface state, other Cisco services can react to the state change, for example:
If the interface state changes, the generic routing and encapsulation (GRE) interface generates IF-MIB notifications (traps)
that report a LinkUp or LinkDown message. The system uses these traps to monitor the connectivity to the DMVPN cloud.
If the interface state changes to down, the Cisco IOS backup interface feature can be initiated to allow the system to use
another interface to provide an alternative path to the failed primary path.
If the interface state changes to down, the system generates an update that is sent to all dynamic routing protocols. The
Interface State Control feature a failover mechanism for dynamic routing when the multipoint GRE (mGRE) interface is down.
If the interface state changes to down, the system clears any static routes that use the mGRE interface as the next hop.
The Interface State Control feature provides a failover mechanism for routing when the mGRE interface is down.
The interface state control feature works on both point-to-point and mGRE interfaces.