If your router running Cisco IOS is fast enough to handle the PPS for the throughput, then use IOS firewall.
If your router is not too powerful and it already has other things running such as NAT, ACL, PBR... or anything else that is process routing vs. route-cache. It may overwhelm the CPU of the router, get a dedicated PIX/ASA to protect the edge.
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...