The problem I am having is comparing the sniffer capture on the inside server to the one on the DMZ server because I think the TCP sequence numbers are being altered. The TCP port numbers appear to be maintained.
Does the PIX alter the TCP sequence numbers? If so does it do so in a predicatble manner?
Also can someone point me to documentation on this behavior?
Thanks for the reply Leo. What I don't understand is if the PIX is always changing the sequence numbers how the end stations are keeping track of them. Is it because the PIX only randomizes the sequence numbers of new sessions and keeps the same sequence throughout the session?
You're right. The inside client doesn't see any difference in TCP sequence number, the PIX presents another sequence number to the DMZ server or outside. The PIX does a sequence number translation. There is a randomizing at the beginning of new session, and this one is kept for the rest of the session.
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...