Cisco Cisco IOS Software Release 12.2(14)S

This document provides configuration guidelines for deploying the GRE Tunnel Keepalive feature in 
Cisco IOS Release 12.2(14)S. It includes the following sections:

The GRE Tunnel Keepalive feature provides the capability of configuring keepalive packets to be sent 
over IP-encapsulated generic routing encapsulation (GRE) tunnels. You can specify the rate at which 
keepalives will be sent and the number of times that a device will continue to send keepalive packets 
without a response before the interface becomes inactive. GRE keepalive packets may be sent from both 
sides of a tunnel, or from just one side.

The functionality of the keepalive command has been expanded to provide you with the ability to take 
down the line protocol of the GRE tunnel interface if the far end becomes unreachable. 

12.2(8)T

This feature was introduced on several platforms. The keepalive command 
was modified to make it available for use on tunnel interfaces.

12.2(14)S

This feature was integrated into Release 12.2(14)S.