That goes for all failover devices such as PIX'es, LocalDirectors etc.
Every time a unit goes from standby to active there is a short time with no connection to whatever users are trying to reach. All connections are also dropped, which can result in timeouts for users.
Since the primary and secondary unit are only selected by the end of the failover cable and only can work on 2 identical units, there is no need to switch back. The performance is exactly the same on both units, so why risk losing maybe important sessions? As I see it, there is no need for such a "switchback" mechanism and I am sure that Cisco feels the same way about this.
Just to confirm what the previous poster said, after the primary or failed PIX comes back up, the currently active PIX does NOT automatically fail over. Why should it. If you want to force the primary to become the active again then you can either do a "failover active" on the primary, or a "no failover active" on the secondary.
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...
[toc:faq]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 and UDP are I...