Using 6.3 this is not possible. However, if you upgrade to 7.0 then you have some more options available such as repeat count or timeout. It's not like 'ping -t' but you can repeat for example over 2billion pings - now that's a lot of pings ;)
btw - I have tested this on FWSM running 3.1(1) <- this is equivelent to PIX 7.0
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...