I'm newbie on the firewall policy configuration. As far as I know, the policy configuration always need to allow both ways. Exm allows services Port1 --> Port2, Port2 --> Port1 in order for both to communication. I've noticed the policy on the internal to wan is always a single policy and it works both way too as from the internal able to reach internet after the nat and flow back to internal.
Pls advise would be greatly appreciated. Many thanks.
For a stateful firewall (such as the Cisco ASA), it keeps track of tcp connections (and udp flows) in its connection table. When traffic is returning in response to an internally-initiated communication, that table finds a connection record and allows the return traffic to transit without requiring matching an access-list.
Only when traffic is initiated from outside does it need an explicit access-list to be allowed into the inside (or other interfaces of higher security level than outside).
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...