Keepalive support for GRE interfaces

Generic routing encapsulation (GRE) tunnel interfaces do not have a built-in mechanism for detecting when a tunnel is down. You can enable keepalive messages to serve as the detection mechanism. When you enable a GRE tunnel interface for keepalive messages, the interface sends out keepalive request packets to the remote endpoint at regular intervals. If the data path forwarding for the GRE tunnel works correctly at all points, keepalive response packets are returned to the originator. These keepalive messages are processed by the Routing Engine.

You can configure keepalive messages on the physical or logical GRE tunnel interface. If configured on the physical interface, keepalive messages are sent on all logical interfaces that are part of the physical interface. If configured on an individual logical interface, keepalives are sent only on that logical interface.