Enabling invalid SPI recovery

An IPsec "black hole" occurs when one IPsec peer fails (for example, a peer can fail if a reboot occurs). One peer fails and loses its SAs with the other peer. When an IPsec peer receives a data packet for which it cannot find an SA, an invalid SPI is encountered. The peer drops the data packet and tries to send an SPI invalid notification to the data originator. This notification is sent by using the IKE SA. Because no IKE SA is available, the notification is not sent. The originating peer continues sending the data by using the IPsec SA that has the invalid SPI, and the receiving peer keeps dropping the traffic.

The invalid SPI recovery feature enables the receiving peer to set up an IKE SA with the originator so that an SPI invalid notification can be sent. Upon receiving the notification, the originating peer deletes the IPsec SA that has the invalid SPI. If the originator has data to send, new SAs will be set up.

Use caution when you enable the invalid SPI recovery feature because using this feature can result in a DoS attack. Attackers can make a great number of invalid SPI notifications to the same peer.

1. Enter system view.

   system-view

2. Enable invalid SPI recovery.

   ike invalid-spi-recovery enable

   By default, the invalid SPI recovery is disabled.