1. Level 3, 4(error, warnings) is the ideal. Levels 5-7 (notification, informational, debug) generate more logs and should be used in case you want to troubleshoot.
2. You should keep as long as possible depending on your policies. Most companies keep the logs for about 6-12 monhts, but it really depends on the company. If your log load is not too much you can keep them for even more.
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...