This error message means that the ASA received a packet that had no SPI (Security Parameter Index) number to encrypt/decrypt the packet. When an IPSec tunnel is established, it assigns an inbound and outbound SPI number.
In your case, it looks as though the ASA has received an encrypted packet from the said peer and is unable to decrypt it due to no matching SPI. After deletion, the remote side should be able to renegotiate new SPI numbers with the ASA (if necessary). There are bugs on similar issues but they are on version 7.2, so I dont think those will be applicable here. If you are initailly able to start the tunnel then there is no configuration problem. The tunnel will automatically renegotiate any time is some problem occurs.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...