It's normal. I guess you're getting information from logon events (authentication failure, Windows 2000 login sucessful, etc) That's because there're some event logs without IP information and traffic used is not IP routed (NetBIOS, p.e.) In this manner, if you look at the raw message you'll see the logon information (username, password, domain controller like reporting device, etc)
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...