I'm using the ASA for anyconnect users and I keep seeing log messages similar to the following:
4 date=Oct 07 2009 Source IP=10.1.1.201 Source Port=17571 Destination IP=10.0.250.18 Destination Port53887 Duplicate TCP SYN from inside:10.1.1.201/17571 to inside:10.0.250.18/53887 with different initial sequence number
The source changes from various server (so far our Anti-virus server, dns, and Active directory servers) the destination appears to be client ip's that have disconnected.
I would like to stop this as it is filling my logs up with spurious information
A duplicate TCP SYN was received during the three-way-handshake that has a different initial sequence number than the SYN that opened the embryonic connection. This could indicate that SYNs are being spoofed. This message occurs in Release 126.96.36.199 and later.
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...