First of all, thanks to everyone who will take the time to read this message. We have a fairly large VPN topology between our primary data center and various customer sites. One site has an 1841 running 12.4(24) Mainline that is logging a rather peculiar error message:
This message is only being experienced at this one site and doesn't seem to be effecting VPN availability or performance. This is more a question out of curiosity than anything. The current findings using Cisco's Error Message Decoder is as follows:
decrypt: mac verify failed for connection id=[dec]
MAC verify processing failed. This may be due to the use of the wrong key by either party during the MAC calculations. Some might consider this a hostile event."
Most others that have experienced this issue usually are able to find a resolution by disabling Fast Switching on the interface(s) involved. I'm curious if anyone else has experienced this issue in a similar deployment. I'm assuming "MAC calculations" in Cisco's description is referring to frame-based CRC values but I'm not receiving any inbound errors on the line. I'm also a little puzzled about the actual nature of this error, as it relates to IPSEC.
Any input would be greatly appreciated.