Understanding Global SPI and VPN Monitoring Features

You can monitor and maintain the efficient operation of your VPN using the following global VPN features:

SPI—Peers in a security association (SA) can become unsynchronized when one of the peers fails. For example, if one of the peers reboots, it might send an incorrect security parameter index (SPI). You can enable the device to detect such an event and resynchronize the peers by configuring the bad SPI response feature.
VPN monitoring—You can use the global VPN monitoring feature to periodically send Internet Control Message Protocol (ICMP) requests to the peer to determine if the peer is reachable.