Someone recently complained to me that he could not send SMTP alerts through the ASA 5510 (8.0(3)12) from their IBM ServeRaid application. I set up a packet capture on both the inside and the outside interfaces and found that the ASA is replacing the HELO command with XXXX and sending it on. Upon further investigation, I discovered that the SMTP HELO command had been segmented at the TCP layer such that the first packet contained the "H" and the second packet contained the rest of the command.
This raises a couple of questions. The first question is why in the world the command wasn't transported in a single TCP segment. At this point I am attributing it to a flaky SMTP client. The second question I have is, can this behavior be accommodated? Is there a way to get the ASA to reassemble before inspection takes place?
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...