I think discards are incremented when the concentrator receives an IP or ARP packet that either has some error or we don't need to process (not listening for) or can't process (Interface down, no route to destination, no ARP entry for dest, etc.). Basically this is not a problem, what it means is if your concentrator is connecting to a flat network that there are other devices connecting to, the Discards is incremented every time when it gets an IP or ARP packet but not destined to the concentrator itself.
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...