GRE Keepalive

GRE keepalive is used to monitor the tunnel destination. Unlike a tunnel probe that is only capable of monitoring the state of the specified IP address, GRE keepalive both monitors the state of the IP address and whether the end-point was able to decapsulate the tunnel packet. A failed keepalive causes the tunnel to transition to the down state.

When enabling GRE keepalive, specify the transmit interval that determines the period between the transmission of keepalive messages and the number of GRE keepalive retries.

Use the tunnel keepalive command, in tunnel configuration mode, to enable GRE keepalive on a GRE IPv4 over IPv4 tunnel.