It is static because the translation is not dynamically created when traffic goes through the firewall. This a permanent translation that you want all the time.
The purpose is because of an oddity with the pix/asa device. To allow traffic from a lower to a higher security level interface you need to
i) allow it in an access-list
ii) have a NAT statement for it
On most other firewalls you only NAT if you want to represent one address as another address. On pix/asa even if you don't want to change the address because of ii) you must have a nat statement and that is why you have it. It is almost a way of saying to the pix/asa i don't want to NAT for 172.16.32.0.
As i say it is an oddity of the pix/asa firewalls.
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...