The standby address should be unique to the failover firewall. You should not use an IP address already in use by another device. And yes, it is possible to ping the standby ip address, if icmp is allowed on that interface. i.e. "icmp permit  "
You can even login to the secondary firewall using the failover IP address, but do not change the configuration. It's useful for when you want to intentionally failover the firewall. (Login to the secondary and run "failover active".)
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...